Draper 64573, O20M/3C Instruction Booklet

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INSTRUCTION OVERVIEW FOR

Oscilloscope

& Multimeter

Stock No.64573 Part No.O20M/3C

IMPORTANT: PLEASE READ THESE INSTRUCTIONS CAREFULLY TO ENSURE THE SAFE AND

EFFECTIVE USE OF THIS PRODUCT.

GENERAL INFORMATION

These instructions accompanying the product are the original instructions. This document is part of the product, keep it for the life of the product passing it on to any subsequent holder of the product. Read all these instructions before assembling, operating or maintaining this product.

This manual has been compiled by Draper Tools describing the purpose for which the product has been designed, and contains all the necessary information to ensure its correct and safe use. By following all the general safety instructions contained in this manual, it will ensure both product and operator safety, together with longer life of the product itself.

AlI photographs and drawings in this manual are supplied by Draper Tools to help illustrate the operation of the product. Whilst every effort has been made to ensure the accuracy of information contained in this manual, the Draper Tools

policy of continuous improvement determines the right to make modifications without prior warning.

1. TITLE PAGE

1.1 INTRODUCTION:

USER MANUAL FOR:

OSCILLOSCOPE & MULTIMETER

Stock no. 64573 Part no. O20M/3C

1.2 REVISIONS:

Date first published March 2015

As our user manuals are continually updated, users should make sure that they use the very latest version.

Downloads are available from: http://www.drapertools.com/b2c/b2cmanuals.pgm

DRAPER TOOLS LIMITED WEBSITE: drapertools.com HURSLEY ROAD PRODUCT HELPLINE: +44 (0) 23 8049 4344 CHANDLER’S FORD GENERAL FAX: +44 (0) 23 8026 0784 EASTLEIGH HAMPSHIRE SO53 1YF UK

1.3 UNDERSTANDING THIS MANUALS SAFETY CONTENT:

WARNING! Information that draws attention to the risk of injury or death.

CAUTION! Information that draws attention to the risk of damage to the product or

surroundings.

Copyright © Draper Tools Limited. Permission is granted to reproduce this publication for personal & educational use only. Commercial copying, redistribution, hiring or lending is prohibited. No part of this publication may be stored in a retrieval system or transmitted in any other form or means without written permission from Draper Tools Limited.

In all cases this copyright notice must remain intact.

Brief introduction ..................................................................................................... 3

Package Checklist .................................................................................................... 5

Chapter I、Recognizing this product ....................................................................... 6

1、 Product Description .................................................................................. 6

1.1 Front Panel ...................................................................................... 6

1.2 Measurement port ............................................................................ 7

2、Panel keyboard and display interface ......................................................... 8

2.1 Panel function keys ......................................................................... 8

2.2 Display Interface ............................................................................. 9

3、The main measurement function and menu structure .............................. 10

3.1 The main measurement function ................................................... 10

3.2 Menu structure ............................................................................... 10

Chapter II、Use instrument ................................................................................... 19

1、Oscilloscope ............................................................................................. 19

1.1 Test connection ............................................................................. 19

1.2 Oscilloscope measurement applications ........................................ 20

2、DMM ........................................................................................................ 24

2.1 Test the connection ........................................................................ 24

2.2 Multimeter ..................................................................................... 24

Chapter III、The Instrument in the automotive fault diagnosis ............................ 26

1、 Safety Precautions .................................................................................. 26

2、 Introduction ............................................................................................ 28

2.1 Primary Signal Types Found In Modern Vehicles ........................ 28

2.2 Critical Characteristics Of Automotive Electronic Sig n als ........... 30

2.3 The Golden Rule Of Electronic System Diagnosis ....................... 30

2.4 Signal Probing With An Oscilloscope .......................................... 31

3、 Automotive Testing ................................................................................ 32

3.1 Into the automotive component testing m enu ............................... 32

3.2 Sensor Test .................................................................................... 33

3.3 Ignition System Test ...................................................................... 91

3.4 Auxiliary Test .............................................................................. 106

3.5 Diesel menu ................................................................................. 120

Chapter IV、Interface and Software .................................................................... 124

Chapter V、 Maintenance and repair .................................................................. 126

Chapter VI、Disposal .......................................................................................... 128

Chapter VI、Technical Specifications ...............................................................

129

Brief introduction

The Automotive Oscilloscope & Multimeter is a 20MHz digital storage oscilloscope, 6000 words True RMS Digital Multimeter, automotive electronics measurement functions integrated multifunctional handheld instrument, ideal for field use.

The main function

• 3-channel, 20MHz digital storage oscilloscope

• True 6000 words RMS digital multimeter

• Automotive electronic measurement: sensors, actuators, ignition systems, electrical

component testing

Features

• 100MSa / s real-time sampling rate, 20MHz real-time bandwidth

• Automotive electrical measurements, 51 kinds of automotive standards Reference

Waveform

• Automatic tracking measurement: automatic tracking based on external input signal to

adjust the vertical amplitude \ horizontal time base and trigger stalls, w ithout human intervention

• Large dynamic measurement range: no extended probe leads directly measure range from

10mV/div to 500V/div

• Screen can display 4 measurement parameters：the user can choose RMS, peak, average,

frequency, period, in 22 kinds of parameters as needed, etc.

• Two kinds of cursor measurement mode selection

• 320 * 240 dot TFT LCD,

• Built-in battery, AC and DC

• Recorder --- continuous track record up to 12 hours of event

• Standard USB interface, through the PC software can easily communicate with a computer

for data analysis and test results archive

5. HEALTH & SAFETY INFORMATION

5.1 GENERAL SAFETY INSTRUCTIONS

For your own safety and the safety of others, and to prevent damage to the equipment and vehicles, read this manual thoroughly before operating your scanner. The safety messages presented below and throughout this user’s manual are reminders to the operator to exercise extreme care when using this device. Always refer to and follow safety messages and test procedures provided by vehicle or equipment manufacturer. Read, understand and follow all safety messages and instructions in this manual. Safety Message Conventions Used We provide safety messages to help prevent personal injury and equipment damage. Below are signal words we used to indicate the hazard level in a condition.

DANGER

Indicates an imminently hazardous situation which, if not avoided, will result in death or serious injury to the operator or to bystanders.

WARNING

Indicates a potentially hazardous situation which, if not avoided, could result in death or serious injury to the operator or to bystanders.

CAUTION

Indicates a potentially hazardous situation which, if not avoided, may result in moderate or minor injury to the operator or to bystanders.

5.2 SPECIFIC SAFETY INSTRUCTIONS

Always use your oscilloscope as described in the user’s manual, and follow all safety messages.

WARNING

Do not route the test cables in a manner that would interfere with driving controls. Do not exceed voltage limits between inputs specified in this user’s manual. Always wear approved goggles to protect your eyes from propelled objects as well as hot or

caustic liquids. Fuel, oil vapours, hot steam, hot toxic exhaust gases, acid, refrigerant and other debris

produced by a malfunctioning engine can cause serious injury or death. Do not use the scanner in areas where explosive vapour may collect, such as in below-ground pits, confined areas, or areas that are less than 18 inches (45 cm) above the floor.

Do not smoke, strike a match, or cause a spark near the vehicle while testing and keep all sparks, heated items and open flames away from the battery and fuel / fuel vapours as they are highly flammable.

Keep a dry chemical fire extinguisher suitable for gasoline, chemical and electrical fires in work area.

Always be aware of rotating parts that move at high speed when an engine is running and keep a safe distance from these parts as well as other potentially moving objects to avoid serious injury.

Do not touch engine components that get very hot when an engine is running to avoid severe burns.

Block drive wheels before testing with engine running. Put the transmission in park (for automatic transmission) or neutral (for manual transmission). And never leave a running engine unattended.

Do not wear jewellery or loose fitting clothing when working on engine.

Package Checklist

The following items are included in this Instrument package.

No.

Description

Quantity

Remark

Oscilliscope & Multimeter

Li Battery Pack

installed 3 AC/DC Power Adapter

Oscilloscope Probes

1 5

Multimeter Test Leads

(red, yellow） 6 BNC-banana adapter

1 7

The back of the input pins (red, yellow,

black)

Optional

Alligator Clips: (red, yellow and black)

Optional 9 Secondary Pick-up

Inductive Pick-up

Current Probe

Optional

Diesel probe set

Optional

Temperature probe

Optional

Users Manual

Chapter I.Recognizing this product

1、 Product Description

1.1 Front Pane

The Product is a handheld portable products, AC and DC power supply, 3.7V lithium battery inside the instrument; external AC-DC adapter with 220/5V can provide external power and charge the lithium battery inside the instrument.

Side port 320×240 TFT AC-DC adapter LCD screen Port and USB port

Panel and function keys

Measurement ports

1.2 Measurement port

CHA、CHB：

CHA、CHB is used f o r all single channel measurements, can be con nected through the banana \BNC conversion by oscilloscope probe or with dual banana plug . In SCOPE mode you can use the instrument as a dual trace oscilloscope with CHA and CHB connected.

COM：Oscilloscope and multimeter measurements common ground port

TRIG:

1）Oscilloscope mode：Used in SCOPE mode to trigger (or start) acquisitions from an external source 2）Multimeter mode：DC voltage \ AC voltage \ Resistance \ Continuity \ Diode \ capacitance \ current measurement input ports Note: 1、Note that each port safety limit, do not exceed the maximum test range。 2、The multimeter testing current mode, you must use the current probe 3、Note that proper grounding

A ground loop can be created when you use two ground leads connected to different ground potentials. This can cause excessive current through the grounding leads

2 Panel keyboard and display interface

2.1 Panel function keys

key

Description

Function keys：The function assigned to each key is indicated by the Function Key Label displayed above the key on the bottom display

In most of the menu to return to the previous menu

Run \ hold, lock screen

Sets automatic ranging on and off (toggle). When on, the top right display shows AUTO. When this function is set on, it searches for the best range and time base settings and once found it tracks the signal. When this function is off, you sh o u ld manually control ranging.

Oscilloscope mode, press the button, so that the corresponding channel's Voltage Range effectively

Oscilloscope mode，Press the button, making the timebase adjustment effectively

Oscilloscope mode, select the trigger level \ trigger edge \ trigger source \ trigger mode

Function key to switch between the main menu

Move up and down a waveform \ trigger level \ voltage cursor； Manually change the sensitivity level of the base, multimeter voltage \ resistance \ capacitors \ Current gear change; Can also be used as a return to the previous menu key

Moves a waveform or Time cursor right and left; Ranges amplitude up and dow or Change the trigger edge; Move around and select the current coefficient bits，Menu selection

Turns the power on and off (toggle). When you turn the power on, previous settings are activated.

Frequency Counter

2.2 Display Interface

2.2.1 Oscilloscope

Trigger Mode Time Zero oscilloscope\ External power Run \ Hold Automotive communication status

Battery indicator Parameter display

Waveform display Trigger level CHA zero level

CHB zero level

Vertical / horizontal range Menu Module

Indicate trigger slope (rising or falling).

2.2.2 DMM

State display area

Data display area

The current gear, measuring state

Measurement items

B waveform and adjust the vertical range

3 The main measurement function and menu structure

3.1 The main measurement function

The instrument has the oscilloscope, multimeter, automotive  component three main measurement function, wherein, the oscilloscope and multimeter are two independent measuring function.

Automotivecomponent measurement is an extension of the application on the basis of on the oscilloscope measurements. It is the automotive sensors, actuators, fuel injectors, and dozens of other electrical components measured waveform and the corresponding measurement settings are stored in the instrument, when the user measurements corresponding items directly recall the settings and Reference Waveform, greatly facilitate on-site testing

3.2 Menu structure

The menu has two major main menu module, divided into two screen displayPress key switch, each screen 5 menu module Pow The main menu 1

The main menu 2

er On

3.2.1 Oscilloscope menu operation

• The vertical range

1Move up and down channel A \

The main menu 

or Effective corresponding channel A, or channel B.

or Move up and down waveforms.

or Adjust the vertical range Adjust the vertical range10mV/div500V/div(No probe attenuation1:1

2）Channel A\B other settings

Power On

Enable / disable the channel CHA / CHB； The instrument can display the input A or B input signal waveform in dual-channel oscilloscope

mode, the input A and input B signals simultaneously displayed. If the user wants to measure individual signals, selectable s in gle -channel oscilloscope mod e, simply connect the input A that to the input B closed; Conversely, if the user wants to simultaneously measure two signals ,directly using dual-channel oscilloscope mode while connected to input A, input B.

Select CHA / CHB signal coupling, DC coup/AC coup DC Coupling allows you to measure and display both the DC and AC components of a signal.

AC Coupling blocks the DC component and passes the AC component only.

Select the CHA/CHB bandwidthlimitBW 20MHz/BW 10KHz

There are cases where you may want to filter out noises in order to see a better signal. This can be especially true when ignition noise is present. The instrument provides a noise filter for each input chann e l, which reduces the bandwidth from its normal 20MHz to 1 0KHz. Yo u can enable or disable CH A Filter or CH B Filter using the INSTRUMENT SETUP menu. When enabled, the FILTER indicator appears on the scre e n.。

Select the CHA/CHB voltage probe attenuation coefficient

V:×1/ V:×10/ V:×100/ V:×1000/ V:×10000

Or select the CHA/CHB current probe conversion coefficient

1mA/mV;10mA/mV;0.1A/mV;1A/mV;10A/mV

You can according to the probe type CHA or CHB (voltage probe, current probe) to select its corresponding attenuation factor or conversion factor

• Time base range

Main Menu

Or Effective timing adjustment function ， or Horizontal compression expansion wave Time base range：10ns/div󺷏2h/div

• Trigger

TRIGGER is a set of conditions that determine whether and when acquisitions start. The following will determine the trigger conditions a) Trigger Edge；b）Trigger Level；c）Trigger Source；d）Trigger mode 1）Changing the trigger edge and trigger level Main Menu

or Effective trigger function or Move up and down the trigger level or Changing the trigger edge ,If you s elect , trigger occurs at a rising(positive) edge of the signal. If you select , trigger occurs at a falling(negative) edge of the sig n al. 2） Change the trigger mode and select the trigger source Main Menu to continue or Go to Trigger Set menu

Select CHA trigger； Select CHB trigger； Select the external signal as the trigger source； Select trigger mode: AUTO \ NORMAL \ SINGLE

AUTO：

The instrument always performs acquisitions, i.e., it always displays the signals on the input.

NORMAL：If NORMAL is selected, a trigger is always needed to start an acquisition SINGLE： SINGLE allows you to perform single acquisition to snap events that occur only once. is

used to start a next single acquisition.

Return to the previous menu

• Cursor

A cursor is a vertical line or a horizontal line placed over the displayed waveform to measure values at certain points. The instrument can measure signal details by using C ursors ,Single cursor mode is suitable for absolute measurements, dual cursor suitable relative measurement。

1）Single cursor measurement mode

Main Menu

Effective single cursor mode, a red horizontal line and a red vertical line appears on the screen, representin g the VOLTS and TIME cursors for measuring relative to the reference (amplitude and time) offset value。 or Move the cursor up and down the VOLTS cursor ; higher than the zero level line is positive, below the zero level line is negative

or To move the TIM E cursor left and right; negative at a time reference on the left, at the right time basis is positive。

Note: a single cursor mode is effective for channel A, channel B can be read out at the

same time, the double channel value

2）Double cursor measurement model

Continue Into double cursor measurement mode

Effective CHA or CHB cursor The cursor 1 effective， or Move up and down

VOLTS cursor； or to

move the

TIME cursor left and right。

The cursor2 effective， or Move up and down

VOLTS cursor； or to

move the

TIME cursor left and right。

In this mode, the two cursor is o nly valid for the current ch ann el, two cursor each channel for the same type of cu rsor, or VOLTS cursor , or TIME cursor. Each cursor to measure the relative value of the deviation between the reference and the two cursors relative

Two cursor mode can be converted to each other。

In the VOLTS cursor mode, or converted to TIME cursor;

In the TIME cursor mode, or converted to VOLTS cursor. or

Return to the previous menu

• Display Set

Main Menu

Display Set menu

1）Persist

When a new waveform display, before the waveform on the screen does not disappear immediately, but continue for some time, n amely persistence time, by setting the persistence time waveform display allows more continuous, and then get a similar analog oscilloscope display

Select the persist time 1Second\2SSecond\5SSecond\Infinite

Return to the previous menu

Average

2） The average acquisition mode can reduce the display signal of random and unrelated noise, sampling value in real-time sampling mode, and then repeatedly sampled waveform average calculation In the Display Set menu

Select the average time 4 times \ 164 times \ 324 times \ 64times

Return to the previous menu

3）Reference Waveform

The user can be real-time measured waveform as the standard waveform storage, so the next measurement comparison In the Display Set menu

Turns the CHA Reference Waveform on and off (toggle). Turns the CHB Reference Waveform on and off (toggle) Storage Reference Waveform Recall Reference Waveform or

Return to the previous menu

• Read Out

Main Menu

Set out parameter types 1 to 4

Select the active channel parameter readout(CHA\CHB) or Select the type of read-out Open \ close Read out on screen display

Measurement results can be displayed as numeric values (referred to as readings) and waveform. The types of

readings depend on the test taking place: Maximum, minimum, peak, average, RMS and other 21 kinds of

parameters for selection

Or Return to the previous menu

• Save Call Main Menu

Save Call Menu

1）Save Call Set

Save Call Menu

In the

Increase

Save set location Decreased Save set location or ok

In the

Increase Note: a total of 10 storage locations can be used, the factory settings in the tenth memory locations

2）Save Call Waveform

In the

Increase

In the

Increase

Save Call Menu

Call set location Decreased Call set location or ok 

Or Return to the previous menu

Save Call Menu

Save Data location Decreased Save Data location or ok

Save Call Menu

Call Data location Decreased Call Data location or ok

Or Return to the previous menu

• User Options

Main Menu

User Options Menu

Select Language \English Open \ close the screen grid

Increase the brightness of the LCD Reduce the brightness of the LCD or Or Return to the previous menu

Increase the auto-off time Reducing the auto-off time or Or Return to the previous menu

• System

Main Menu

Normal ,Oscilloscope mode Component, automotive electronic measurement, detailed operation, see the application of automotive electronics diagnostics and fault section DMM AdjustThis function is not open to users

3.2.2 DMM MENU

Main Menu

System Menu

DMM Menu

Select the DC voltage \ AC voltage Manually adjust the voltage range 600mV\6V\60V\600V\1000V Select the Resistance \ Continuity \ Diode \ Capacitance measurements

Note: Multimeter automatic measurement mode by default

Manually adjustable resistance range:600Ω\6KΩ\60KΩ\600KΩ\6MΩ Manually adjustable capacitance range:6nF\60nF\600nF\6uF\60uF\600uF\6mF Select DC \ AC current Set current coefficient Select the position to be adjusted. Inc Increased or Decrease the number

Return to the previous menu

 Exit multimeter mode, return the osc illosco pe to m e asu re

Chapter II、Use instrument

1 Oscilloscope

SCOPE mode provides a display of signal patterns from either CH A or CH B over times ranging from 10ns to 2Hours per division, and for voltage ranges from 10mV to 500 V full scale.

Using Single and Dual Input Scope Mode The instrument can be configured to show scope displays for either CH A or CH B signals: In DUAL INPUT SCOPE mode, both CH A and CH B may be displayed at the same time.

Use SINGLE INPUT SCOPE mode if you want to measure a single signal, INPUT B is turned off. Use DUAL INPUT SCOPE mode if you want to simultaneously measure two signals.

1.1 Test connection

The instrument has two kinds of test connection options 1）Use BNC-banana plug adapter head (note polarity), using an oscilloscope probes or

BNC cable

2） Use a multimeter pen directly

Note：

The oscilloscope bandwidth can be up to 20MHz, while the banana plug line width ≤ 6MHz, so when measuring the high frequency signals in order to guarantee the measurement precision, using the first connection recommendation。

1.2 Oscilloscope measurement applications

• Automatically capture waveform

When you enter the scope mode, the instrument automatically optimizes vertical range, time base, and trigger settings to create a stable display. (Auto ranging is default)。

Single-channel measurements Dual-channel measurement

Automatic mode, the vertical / horizontal sensitivity status indication：

When you press one of the Voltage and Time control keys, the instrument switches to manual control of range and trigger settings Manually set： move up and down CHA Waveform Change the CHA voltage range move up and down CHB Waveform

Change the CHB voltage range Moving the waveform to the left and right Change the Time base

Channel set in automatic mode

Trigger set in the automatic mode

Users can also manually change the settings

• Read Out

In Read Out Menu Settings and select the param e te r t yp e (CHA or CHB)

Parameter readout

• Waveform display processing

In the Disp Set menu Select the persistence and the average function

1） persistence

Infinite persistence

2） average

average 32 times

• Cursor measurements

In the main menu to start a single cursor mode; continue to start dual cursor mode

1）Single cursor mode

Move the voltage cursor up and

down

Move the Time cursor left and right

2）

Dual cursor mode

In the voltage cursor， or Converted into time cursor In the Time cursor， or Converted into voltage cursor

Select Cursor 1

Select Cursor 2

Move the cursor up and down

Move the cursor left and right

• Scanning and recorder function

Horizontal base in 200ms/div, or slower, the oscilloscope into a rolling screen status indication "scan", this way, the waveform scroll from left to right to update, easy to measure low-frequency signals in this manner and long period of mutation and very narrow pulse signal

Scan

Horizontal base in 10s/div, or slower, the oscilloscope into recording mode, the screen status indication "Record", the o s cillo s co p e can record the maximum an d minimum values, you can record up to 24 hours of the event。

Record

2、DMM

2.1 Test the connection

In the TRIG terminal and COM terminal directly connected multimeter pen or curre nt prob e

2.2 Multimeter

• DC voltage measurement

Right is automatic measurement

Manually change gears

600mV\6V\60V\600V\1000V

• AC voltage measurement

Right is automatic measurement

Manually change gears

600mV\6V\60V\600V\1000V

• Resistance measurement

Right is automatic measurement

Manually change gears

600Ω\6KΩ\60KΩ\600KΩ\6MΩ

• Continuity measurement

• Diode measurements

The maximum measured diode voltage drop of 3V

• Capacitance measurement

Right is automatic measurement

Manually change gears

6nF\60nF\600nF\6uF\60uF \600uF\6mF

• Current Measurement Use this menu option to test current with a current probe. (optional accessory) Select the current coefficient according of the current probe “***A/V” Don’t forget to set the Current Probe to zero before using it for measurements.

Chapter III 、 The Instrument in the automotive fault diagnosis

1、Safety Precautions

CAUTION：

When handing any extremely high voltage signals, e.g. the signals generated from the sparkplugs, NEVER PUT ANY TEST LEADS (Either the Red or Yellow test leads Or the Secondary ignition probe lead Or Power Cable from Cigarette Lighter) CONNECTED TO THE SCOPEINTHE AREAS NEAR THOSE STRONG SIGNALS. If so, the scope can be damaged or worked improperly.

CAUTION

Avoid Electrical Shock:

• Make sure that the vehicle to be tested is at a safe potential before making any measurement

connections.

• Connect the COM input of the instrument to vehicle ground before clamping the standard

SECONDARY PICKUP (supplied) o n the ignition wires. T h is ground connection is required IN ADDITION TO the normal measurement ground connections.

• Do not touch ignition coils, coil terminals, and spark plugs while operating. They emit high

voltages.

• Do not puncture an ignition wire to connect the instrument, unless specifically instructed by

vehicle manufacturer.

• Be sure the ignition is in the OFF position, headlights and other accessories are off, and doors

are closed before disconnecting the battery cables. This also prevents damage to on-board computer systems.

• Avoid working alone.

• Inspect the test leads for damaged insulation or exposed metal. Check test lead continuity.

Replace damaged leads before use.

• Do not use the instrument if it looks damaged.

• Select the proper function and range for your measurement.

• When using the probes, keep your fingers away from p robe contacts. Keep your fingers behind

the finger guards on the probes.

• Disconnect the live test lead before disconnecting the common test lead.

• Do not perform internal service or adjustment of this instrument unless you are qualified to do

• Use only the standard test leads set supplied with the instrument.

• Do not use conventional exposed metal BNC or BANANA PLUG connectors.

• Use only one ground connection to the instrument (GROUND LEAD of the CH A’s shielded

test lead).

• Remove all probes and test leads that are not in use.

• Connect the power adapter to the AC outlet before connecting it to the instrument

Avoid Burns:

• Do not touch hot exhaust systems, manifolds, engines, radiators, sample probe, etc.

• Do not remove radiator cap unless engine is cold. Pressurized engine coolant may be hot.

• Wear gloves when handling hot engine components.

• Use a suitable battery carrier when transporting batteries

VEHICLE SERVICE MANUALS

This instrument tells how to hook up it to the selected vehicle components to be tested. However, it is strongly recomm en ded that you consult the manufacturer’s service manual for your vehicle before any test or repair procedures are performed in order to get the color of the wire or the PCM’s pin number from a wiring diagram. For availability of these service manuals, contact your local car dealership, auto parts store, or bookstore, The following companies publish valuable repair manuals.

2、Introduction

2.1 Primary Signal Types Found In Modern Vehicles

Once you become familiar with basic vehicle waveforms it will not matter how new or old the vehicle is, or even who manufactured the vehicle. You will be able to recognize signals that do not look right.。

Automotive electronic signals can be divided into analog signals and digital signals. Further broken down into five basic types, nam ely DC signal, the AC signal, frequency modulated signal, the pulse width modulated signal and serial data signals

DC signal AC signal frequency modulated signal

pulse width modulated signal serial data signals

1）DC Signals

The types of sensors or devices in a vehicle that produce DC signals are:

• Power Supplies - Battery voltage or sensor reference voltages created by the PCM.

• Analog sensor signals-engine coolant temperature, fuel temperature, intake air temperature,

throttle position, EGR pressure and valve position, oxygen, vane and hot wire mass airflow sensors, vacuum and throttle switches and GM, Chrysler and Asian manifold absolute pressure (MAP) sensors

2）Alternating Current (AC) Signals

The types of sensors or devices in a vehicle that produce AC signals are:

• Vehicle speed sensors (VSS)

• Antilock brake system wheel speed sensors (ABS wheel speed sensors)

• Magnetic camshaft (CM P) and crankshaft (CKP) position sensors

• Engine vacuum balance viewed from an analog MAP sensor signal

• Knock sensors (KS)

3）Frequency Modulated Signals

The types of sensors or devices in a vehicle that produce Frequency Modulated signals are

• Digital mass airflow (MAF) sensors

• Ford's digital MAP sensors

• Optical vehicle speed sensors (VSS)

• Hall Effect vehicle speed sensors (VSS)

• Optical camshaft (CM P) and crankshaft (CKP) position sensors

• Hall Effect camshaft (CM P) and crankshaft (CKP) position sensors

4) Pulse Width Modulated Signals

The types of circuits of devices in a vehicle that produce Pulse Width Modulated signals are

• Ignition coil primary

• Electronic spark timing circuits

• EGR, purge, turbo boost, and other control solenoids

• Fuel injectors

• Idle air control motors and solenoids

5) Serial Data (Multiplexed) Signals

The types of circuits or devices in a vehicle that produce Serial Data signals are:

• Powertrain control modules (PCM)

• Body control modules (BCM)

• ABS control modules

• Other control modules with self diagnostics or other serial data l communications capability

2.2 Critical Characteristics Of Automotive Electronic Signals

Only 5 critical characteristics (or information types) given from the Automotive

electronic signals are important because the vehicle’s PCM considers them important.

• Amplitude- The voltage of the electronic signal at a certain point in time.

• Frequency- The time between events, or cycles, of the electronic signal, usually

given in cycles per second (Hertz).

• Shape- The signature of the electronic signal, with its unique curves, contours, and

corners.

• Duty Cycle- The on-time, or relative pulse width of the electronic signal.

• Pattern-The repeated patterns w ithin the signal that make up specific messages, like synchronous pulses that tell the PCM that cylinder #1 is at TDC (Top Dead Center ), or a repeated pattern in the serial data stream that tells the scan tool the coolant temp e ra tu re is 212 F (or 100 C), etc.

2.3 The Golden Rule Of Electronic System Diagnosis

For the vehicle’s computer system to function properly, it must send and receive signals with the critical characteristics it was designed to communicate with.

Each of the primary types of electronic signals use the critical characteristics to establish electronic communication. They each use different combinations of the critical characteristics to communicate. Here’s a list of which critical characteristics each of the primary signal types uses to communicate:

• Direct Current signals use Amplitude only.

• Alternating Current signals use Amplitude, Frequency, and Shape.

• Frequency Modulated signals use Amplitude, Frequency, and Shape.

• Pulse Width Modulated signals use Amplitude, Frequency, Shape, and Duty Cycle.

• Serial Data signals use Amplitude, Frequency, Shape, Duty Cycle, and Pattern.

The list will help to give you a better understanding of which signal types use which critical characteristics to do their electronic communication. The above rules work very well and hold up in most cases, but there are exceptions to its rules. Not many, but a few. It may come as no surprise to some that serial data signals are the most complex signals in the

vehicle. They use all 5 critical characteristics to communicate with. Thus, they take a special analyzer to decode them - one very familiar to most technicians - the scan tool.

2.4 Signal Prob ing With An Osc illoscope

The engine compartment of a running vehicle is a very unfriendly environment for automotive signals to live. Temperature extremes, dirt and corrosion, and electrical leaks, or noises from the high voltage pulses generated from a typical ignition system can produce interference that can contribute significantly to the cause of many driveability problems. When you are probing components, sensors and circuits, be aware that the electrical noises from today’s high output ignition systems can pr o du c e a n R F e n erg y th a t is s imilar to a radio station. Since oscilloscopes are so sensitive, this interference can actually override the signals you are trying to capture and give you a false reading o n th e display. To minimize this possible interference with the oscilloscope, keep these tips and suggestions in mind: Most interference will be picked up by the oscilloscope test leads.

• Route the test leads away from all ignition wires and components whenever possible.

• Use the shortest test leads possible, since other test leads may act as an antenna and increase the potential for interference, especially a t h igh e r fr eq u en c y lev e ls th at a re fo u n d when probing near the vehicles on-board computer.

• With the potential for RF interference in the engine compartment, if possible, use the vehicle chassis as ground when connecting the oscilloscope test leads. In some cases the engine block can actually act as an antenna for the RF signals.

• The test leads are a very important part of any oscilloscope. Substituting other leads in both length and capability may alter the signals on your display.

The oscilloscope can also pick up interference like the test leads.

• Because the oscilloscope circuits are so sensitive, and therefore powerful, do not place the oscilloscope directly on ignition wires or near high energy ignition components, like coil packs.

• If you are using the AC or DC charger/adaptor to power the oscilloscope, keep the external power leads far away from the engine and ignition if possible.

Diesel Glow

INC 3 DEC

3、Automotive Testing

3.1 Into the automotive component testing menu

Power on

Vehicle

F2Cylinders F3Cycles F4Battery F5Engine

ABS

SEnsor(Mag

------------------

MAF

Injector

PFI/MFI

-----------------

Plug

PIP/SPOUT

---------------

DIS Secondary

Power Circuit

----------------

Relative Compress

Select the test project OK

3.2 Sensor Test

3.2.1 Summary

Today's cars have complex sensor network, through the sensors circuits and systems, to obtain information from every part of the car running system, and the information is transmitted to the computerSensor tells the computer how fast the car gohow much is the engine rpm, the engine load is much, the car is in a turn or straight line etc. When all the sensor is working properly, the car is running well, emissions are relatively clean, the efficiency will be higher. However, like other devices, the sensor will be damaged, when it is damaged, the computer can't be maintained effective action required information, at this time, to find out which one sensor is bad, repair or replace it, let the system returns to normal working state.

This section describes how to use automobile oscilloscope to check the sensor in the car, how to check the waveform, how to check and find the faulty sensor.

3.2.2 Sensor Test Project 1）Into the sensor test menu

Main Menu

System Menu

Automotive menu

Sensor menu

Or select measurement project Enter

Return to the previous menu

2Automotive Sensor Type

SENSOR TESTS MENU

ABS Sensor (Mag) O2S Sensor (Zirc) Dual O2 Sensor ECT Sensor Fuel Temp Sensor IAT Sensor Knock Sensor TPS Sensor CKP Magnetic CKP Hall CKP Optical CMP Magnetic

SENSOR TESTS MENU

CMP Hall CMP Optical VSS Magnetic VSS Optical MAP Analog MAP Digital MAF Analog MAF Digi Slow MAF Digi Fast MAF Karman-Vrtx EGR (DPFE)

ABS Sensor-Magnetic

• Theory of Operation

ABS (Anti-lock Brake System) wheel speed sensors generate AC signals with frequency proportional to wheel speed. The amplitude (peak to peak voltage) increases as the wheel speed increases and is greatly affected by air gap between the magnetic tip and the wheel. The ABS computer compares the frequencies and uses this information to maintain wheel speeds while braking.

This test shows the sensor’s output signal or the frequency proportional to wheel speed. The sensor’s output signal should be continuous as long as the wheel rotates. Spikes or distortion of individual output pulses may indicate occasional contact between the sensor and the r wheel.

• Symptoms

AB/  C@ > ? K FE  EF   /  J@ > E8C > <E<I8K@ FE

• Test Procedure

1. Connect the shielded test lead to the CH A input and connect the ground lead of the test lead t o the sensor

output LO or GND and the test lead probe to the sensor output or HI. (Use a wiring diagram for the vehicle being serviced to get the ABS control unit pin number, or color of the wire for this circuit.)

2. Drive vehicle or spin the wheel by hand to generate signal.

When driving vehicle, back probe the connector leading to the sensor. Place the transmission in drive, and slowly accelerate the drive wheels. If the sensor to be tested is on a drive wheel, raise the wheels off the ground to simulate driving conditions. Key OFF, Engine OFF

Enter the measurement setup menu, select test items, automatically the measurement setup of the project

4. Compare ABS sensors on all wheels for similarities.

select measurement project; Enter

• Reference Waveform

Display the current CHA actual measurement

Amplitude and Frequency increase with wheel speed. Output signal should be stable and repeatable without distorted pulses.

value

• Troubleshooting Tips

If the amplitude is low, look for an excessive air gap between the trigger wheel and the pickup. If the amplitude wavers, look for a bent axle. If one of the oscillations looks distorted, look for a bent or damaged tooth on the trigger wheel.

O2S Normal - Zirconia

• Theory of Operation

An O2 sensor provides an output voltage that represents the amount of oxygen in the exhaust stream. The output voltage is used by the PCM to adjust the air/fuel ratio of the fuel mixture between a slightly Rich condition and a slightly Lean condition.

A zirconia-type O2 sensor provides high output voltage (a Rich condition) and low output voltage (a Lean condition).

A titania-type O2 sensor changes resistance as the oxygen content of the fuel mixture changes. This results in a low output voltage (from a Rich condition) and a high output voltage (from a Lean condition). Most Titania O 2 sensors are found on MFI (Multiport Fuel Injection) systems.

A voltage swing between 100mV and 900mV indicates that the O2 sensor is properly signaling PCM to control the fuel mixture.

• Symptoms

Feedback Fuel Control System’s (FFCS’s) no entering Closed Loop operation, high emissions, poor fuel

economy

• Test Procedure

Connect the shielded test lead to the CH A input and connect the ground lead of the test lead to the sensor output LO or GND and the test lead probe to the sensor output or HI. (Get the color of the O2 signal wire or PCM pin number from a wiring diagram.

2. Warm the engine and O2 sensor for 2-3 minutes at 2500RPM, and let the engine idle for 20 seconds.

3. Rev the eng ine rapidly five or six times in 2 second intervals from idle to Wide Open Th rottle (WOT). In order to obtain a clear acceleration and deceleration waveform, probably more ap p ro p r iate to keep the engine speed at 4,000 rpm or less;

4. Enter the measurement setup menu, select test items, automatically the measurement setup of the project

select measurement project; Enter

5. to freeze the waveform on the display to check the maximum O2 voltage, minimum O2 voltage and

response time from Rich to Lean

• Reference Waveform

NOTE

For a Titania-type O2 sensor, change the vertical range to 1V/div.

Display the current CHA actual measurement

The maximum voltage when forced Rich should be greater than 800mV. The minimum voltage when forced Lean should be less than 200mV. The maximum allowable response time from Rich to Lean should be less than 100 ms.

value

• Troubleshooting Tips

The response time increases by aging and poisoning of the O2 sensor.

Peak to peak voltages should be at least 600mV or greater with an average of 450mV.

If the waveform is severely hashy, look for a misfire caused by Rich mixture, Lean mixture, ignition problem, vacuum leak to an individual cylinder, injector imbalance, or car boned intake valves.

IMPORTANT: Don’t use a scan tool at the same time you are analyzing the O2waveform on the instrument. The PCM may go into a different operating strategy when diagnostics are activated by the scan tool.

Dual O2Sensor

• Theory of Operation

Many vehicles utilize dual O2sensors within the Feedback Fuel Control System. Both O2sensors provide an output voltage that represent the amount of oxygen in the exhaust stream respectively before and after the catalytic converter. The leading sensor signal is used as feedback for controlling the fuel mixture. The trailing sensor signal is used by PCM to test efficiency of the catalytic converter. The signal amplitude from the trailing sensor will increase when the efficiency of the catalytic converter declines over years. A good O2sensor located downstream from the catalyst should see much less fluctuations than its upstream counterpart during steady state operation. This is due to the properly operating catalyst’s ability to consume oxygen when it is converting HC and CO, thus dampening the fluctuations in the downstream sensor’s signal. That is, the difference in voltage amplitude from the sensors is a measure for the ability of the catalyst to store oxygen for the conversion of harmful exhaust constituents.

• Symptoms

Emissions test failure, poor fuel economy.

• Test Procedure

1. Connect one shielded test lead to the CH A and the other test lead to the CH B. Connect the ground leads of both test leads to the engine GND’s and one lead probe to the sensor 1 (upstream sensor) output or HI and the other lead probe to the sensor 2 (downstream sensor) output or HI.

2. Enter the measurement setup menu, select test items, automatically the measurement setup of the project

select measurement project; Enter

3. Run the engine until the O2 sensors are warmed to at least 600°F (315°C) in closed loop operation.

4. Run the engine at idle while increasing engine speed.

5. Use this test to check the efficiency of the catalytic converter.

• Reference Waveform

Good O2 sensor's output swing between 100mV and 900mV indicates that the O2 sensor is properly signaling PCM to control the fuel mixture.The fluctuations in the downstream sensor’s signal are much smaller than that of the the upstream sensor. As the catalytic converter “lights off” (or reaches operating temperature) the signal goes higher due to less and less oxygen being present in the exhaust stream as the catalyst begins to store and use oxygen for catalytic conversion.

Display the current CHA CHB actual measurement

Downstream O2sensor voltage rises as converter heats up and begins to use excess oxygen to

• Troubleshooting Tips

ECT (Engine Coolant Temperature) Sensor

• Theory of Operation

Most ECT sensors are Negative Temperature Coefficient (NTC) type thermistors. This mean s they are primarily two wire analog sensors whose resistance decreases when their temperature increases. They are supplied with a 5V V Ref power signal and return a voltage signal proportional to the engine coolant temperature to the PCM. When this instrument is connected to the signal from an ECT sensor, what is being read is the voltage drop across the sensor’s NTC resistor.

Typically, ECT sensor’s resistance ranges from about 100,000 ohms at -40°F (-40°C) to about 50ohms at +266°F (+130°C). The ECT sensor signal is used by the PCM to control closed-loop operation, shift points, torque converter clutch operation, and cooling fan operation.

• Symptoms

No or hard start, high fuel consumption, emissions failure, driveability problems.

• Test Procedure

1.Back probe the terminals on the ECT sensor with the CH A lead and its ground lead.

2. Run the engine at idle and monitor the sensor voltage decrease as the engine warms. (Start the engine and hold the throttle at 2500 RPM until the trace goes across the screen.

3. Enter the measurement setup menu, select test items, automatically the measurement setup of the project

or select measurement project; Enter

When a catalytic converter is totally deteriorated, the catalytic conversion efficiency as well as the oxygen storage capability of the catalytic converter are essentially lost. Therefore, the upstream and downstream O2 sensor signals closely resemble one another on an inactive converter.

at operating temp. here

4. Set the time base to 1m/div to see the sensor’s entire operating range, from stone cold to operating temperature.

5. to freeze the waveform on the display for closer inspection

6. To measure resistance, disconnect the sensor before changing to the GMM mode and then connect the Ground and CH A leads to the terminals on the sensor.

• Reference Waveform

Display the current CHA actual measurement

value

Thermostat opens here

PCM resistors witched in here

Engine

• Troubleshooting Tips

Check the manufacturer’s specifications for exact voltage range specifications, but generally the sensor’s voltage should range from 3V to just under 5V when stone cold, dropping to around 1V at operating temperature. The good sensor must generate a signal with a certain amplitude at any given temperature. . Opens in the ECT sensor circuit will appear as upward spikes to V Ref.

Shorts to ground in the ECT sensor circuit will appear as downward spikes to ground level

Fuel Temp Sensor

• Theory of Operation

Most Fuel Temperature (FT) sensors are Negative Temperature Coefficient (NTC) type thermistors. They are primarily two wire analog sensors whose resistance decreases when their temperature increa se s. Some sensors use their own case as a ground, so they have only one wire, the signal wire. They are supplied with a 5V V Ref power signal and return a voltage signal proportional to the temperature to the PCM. FT sensors usually sense the engine’s fuel temperature in the fuel rail. When this instrument is connected to the signal from a FT sensor, what is being read is the voltage drop across the sensor’s NTC resistor.

Typically, FT sensor’s resistance ranges from about 100,000ohms at -40°F (-40°C) to about 50ohms at +266°F (+130°C)

• Symptoms

Hard start, poor fuel economy, driveability problems

• Test Procedure

1. Back probe the terminals on the FT sensor with the CH A lead and its ground lead.

2. Start the engine and hold the throttle at 2500RPM until the trace goes across the screen.

3. Enter the measurement setup menu, select test items, automatically the measurement setup of the project

or select measurement project; Enter

Set the time base to 50 sec/ div to see the sensor’s entire operating range, from stone cold to operating Temperature.

5. key to freeze the waveform on the display for closer inspection.

6. To measure resistance, disconnect the sensor before changing to the GMM mode and then connect the Ground and CH A leads to the terminals on the sensor

cold, dropping to around 1 to 2

• Reference Waveform

Display the current CHA actual measurement

Engine warmed

up for 8 minutes

value

• Troubleshooting Tips

Check the manufacturer’s specifications for exact voltage range specifications, but generally the sensor’s voltage should range from 3V to just under 5V when stone V at operating temperature. The good sensor must generate a signal with a certain amplitude at any given temperature.

Opens in the FT sensor circuit will appear as upward spikes to V Ref. Shorts to ground in the FT sensor circuit will appear as downward spikes to ground level.

INTAKE AIR TEMP (IAT) Sensor

• Theory of Operation

Most Intake Air Temperature (IAT) sensors are Negative Temperature Coefficient (NTC) type thermistors. They are primarily two wire analog sensors whose resistance decreases when their temperature increases. They are supplied with a 5V V Ref power signal and return a voltage signal proportional to the intake air temperature to the PCM. Some sensors use their own case as a ground, so they have only one wire, the signal wire. When this instrument is connected to the signal from an IAT sensor, what is being read is the voltage drop across the sensor’s NTC resistor. Typically, IAT sensor’s resistance ranges from about 100,000ohms at -40˚F (-40˚C) to about 50ohms at +266˚F (+130 ˚C).

cools, voltage increases

• Symptoms

Poor fuel economy, hard start, high emissions, tip-in hesitation

• Test Procedure

1. Back probe the terminals on the IAT sensor with the CH A lead and its ground lead.

2. When the IAT sensors are at engine operating temperature , spray the sensors with a coo ling spray, a water spray, or evaporative solvent spray and monitor the sensor voltage. Perform this test with the Key ON, Engine Off. The waveform should increase in amplitude as the sensor tip cools.

3.Enter the measurement setup menu, select test items, automatically the measurement setup of the project

or select measurement project; Enter

4 to freeze the waveform on the display for closer inspection.

To measure resistance, disconnect the sensor before changing to the GMM mode and then connect the Ground

and CH A leads to the terminals on the sensor.

• Reference Waveform

Key On Engine Off “Spray” test

Intake Air Temp. Sensor

Key On Engine Off here

Intake Air Temp sensor sprayed with brake cleaner here. As sensor tip

• Troubleshooting Tips

Check the manufacturer’s specifications for exact voltage range specifications, but generally the sensor’s voltage should range from 3 V to just under 5 V when stone cold, dropping to around 1 to 2 V at operating temperature. The good sensor must generate a signal with a certain amplitude at any given temperature. Opens in the IAT sensor circuit will appear as upward spikes to V Ref.

Shorts in the IAT sensor circuit will appear as downward spikes to ground level.

Knock Sensor

• Theory of Operation

AC sign al generating Knock Sensors are pie zo electric devices that sense vibration or mechanical stress ( knock) f rom engine detonation. They are quite different from most other AC signal generating automotive sensors that sense the speed or position of a rotating shaft.

Engine detonation resulting from over advanced ignition timing ca n cause severe engine damage . Knock sensors supply the PCM (sometimes via a spark control module) with Knock detection so the PCM can retard ignition timing to prevent further Knocking.

• Symptoms

No AC signal generation at all from Knock Sensors.

• Test Procedure

1. Connect the CH A lead to the sensor output or HI and its ground lead to the engine block or the sensor wire labeled LO (if internally grounded)

Enter the measurement setup menu, select test items, automatically the measurement setup of the project

or select measurement project; Enter

Test 1: With the Key On, Engine Running, put a load on the engine and watch the Scope display. The peak voltage and frequency of the waveform will increase with engine load and RPM increment. If the engine is detonating or pinging from too much advanced ignition timing, the amplitude and frequency will also increase. Test 2: With the Key On, Engine Off, tap the engine block lightly near the sensor with a small hammer or a ratchet extension. Oscillations will be displayed immediately following a tap on the engine block. The harder the tap, the larger the amplitude of the oscillations.

• Reference Waveform

Typical Knock Sensor

test. Note signal goes above and below zero volts(AC).Logged during slight acceleration

• Troubleshooting Tips

Knock sensors are extremely durable and usually fail from physical damage to the sensor itself. The most common type of Knock Sensor failure is not to generate a signal at all due to its physical damage, when the waveform stays flat even if you rev the engine or tap on the sensor. In this case, check the sensor and the instrument connections; make sure the circuit is not grounded, then condemn the sensor.

Throttle Position Sensor (TPS)

•

Theory of Operation

A TPS is a variable resistor that tells the PCM the position of the throttle, that is, how far the throttle is open, whether it is opening or closing and how fast. Most throttle position sensors consist of a contact connected to the throttle shaft which slides over a section of resistance material around the pivot axis for the movable contact.

The TPS is a three wire sensor. One of the wires is connected to an end of the sensor’s resistance material and provides 5 V via the PCM’s V Ref circuit, another wire is connected to the other end of the resistance material and provides the sensor ground (GND). The third wire is connected to the movable contact and provides the signal output to the PCM. The voltage at any point in the resistance material is proportional to the throttle angle as sensed through the movable contact.

The voltage signal returning to the PCM is used to calculate engine load, ignition timing, EGR control, idle control and other PCM controlled parameters such as transmission shift points. A bad TPS can cause hesitation, idle problems, high emissions, and Inspection/ Maintenance (I/M) test failures.

Generally, throttle position sensors produce just under 1 V with the throttle closed and produce just under 5 V with the throttle wide open (WOT). The PCM determines the sensor’s performance by comparing the sensor output to a calculated value based on MAP and RPM signals.

• Symptoms

Hesitation, stall at stops, high emissions, I/M test failures, transmission shifting problems.。

• Test Procedure

1. Connect the CH A lead to the output or signal circuit of TPS and its ground lead to the TPS’s GND.

2. Enter the measurement setup menu, select test items, automatically the measurement setup of the project

or select measurement project; Enter

3. With the Key On, Engine Running, slowly sweep the throttle from closed to the wide open position (WOT) and

then the closed position again. Repeat this process several times.

Closed Throttle

• Reference Waveform

Wide Open Throttle

Closed Throttle

• Troubleshooting Tips

Check the manufacturer’s specifications for exact voltage range. Generally, the sensor output should range from just under 1 V at idle to just under 5 V at wide open throttle (WOT). There should be no breaks, spikes to ground or dropouts in the waveform.

Dropouts on the slopes of the waveform indicate a short to ground or an intermittent open in the sensor’s carbon track (resistance materials). The first 1/8 to 1/3 of the sensor’s carbon track usually wears out most because this portion is most used while driving. Thus, pay particular attention to the waveform as it begins to rise.

Magnetic Crankshaft Position (CKP) Sensor

• Theory of Operation

The magnetic CKP sensors are AC signal generating analog sensors. They generally consist of a wire wrapped, soft bar magnet with two connections. These two winding, or coil, connections are the sensor’s output terminals. When a ring gear (a reluctor wheel) rotates past this sensor, it induces a voltage in the winding. A uniform tooth pattern on the reluctor wheel produces a sinusoidal series of pulses having a consistent shape. The amplitude is proportional to the rotating speed of the reluctor wheel (that is, the crankshaft or camshaft). The frequency is based on the rotational speed of the reluctor. The air gap between the sensor’s magnetic tip and the reluctor wheel greatly affects the sensor’s signal amplitude.

The PCM uses the CKP sensors to detect misfire. When a misfire occurs, the amount of time it takes for a waveform to complete its cycle increases. If the PCM detects an excessive number of misfires within 200 to 1000 crankshaft revolutions, a misfire code (OBD II DTC) is set.

• Symptoms

No or hard start, intermittent misfire, driveability problems

• Test Procedure

1. Connect the CH A lead to the sensor output or HI and its ground lead to the sensor output LO or GND.

2. With KOER (Key On, Engine Running), let the engine idle, or use the throttle to accelerate or decelerate the engine or drive the vehicle as needed to make the driveability, or emissions, problem occur.

3. Enter the measurement setup menu, select test items, automatically the measurement setup of the project

or select measurement project; Enter

• Reference Waveform

The amplitude and frequency increase with engine speed (RPM). The amplitude, frequency and shape should be all consistent for the conditions (RPM, etc.), repeatable (except for “sync” pulses), and predictable. Generally, the oscillations may not be perfect mirror images of each other above and below the zero level mark, but they should be relatively close on most sensors.

• Troubleshooting Tips

Make sure the frequency of the waveform is keeping pace with engine RPM, and that the time between pulses only

changes when a “sync” pulse is displayed. This time changes only when a missing or extra tooth on the reluctor

wheel passes the sensor. That is, any other changes in time between the pulses can mean trouble. Look for abnormalities observed in the waveform to coincide with an engine sputter or driveability problem.

Before assuring the sensor’s failure, when waveform abnormalities are observed, make sure that a chafed wire or bad wiring harness connector is not the cause, the circuit isn’t grounded, and the proper parts are spinning.

Hall Effect Crankshaft Position (CKP) Sensor

• Theory of Operation

These CKP sensors are classified as “CKP Sensors-Low Resolution” in industry. The Hall CKP sensors are low resolution digital sensors which generate the CKP signal, that is a low frequency (hundreds of Hz) square wave switching between zero and V Ref, from a Hall sensor.

The Hall CKP sensor, or switch, consists of an almost completely closed magnetic circuit containing a permanent magnet and pole pieces. A soft magnetic vane rotor travels through the remaining air gap between the magnet and the pole piece. The opening and closing of the vane rotor’s windows interrupt the magnetic field, causing the Hall sensor to turn on and off like a switch - so some vehicle manufacturers call this sensor a Hall switch.

These sensors operate at different voltage levels depending on the vehicle manufacturers and deliver a series of pulses as the shaft rotates. They are used to switch the ignition and/or fuel injection triggering circuits on and off. The PCM uses the Hall CKP sensors to detect misfire.

•

Symptoms

Long cranking, poor fuel economy, emissions problem.

• Test Procedure

1. Connect the CH A lead to the sensor output or HI and its ground lead to the sensor output LO or GND.

2. Key On, Engine Cranking, or, Key On, Engine Running ,use the throttle to accelerate or decelerate the engine or drive the vehicle as needed to make the driveability, or emissions, problem occur.

3. Enter the measurement setup menu, select test items, automatically the measurement setup of the project

or select measurement project; Enter

the shapes repeatable and predictable.

•

Reference Waveform

• Troubleshooting Tips

The duty cycle of the waveform changes only when a “sync” pulse is displayed. Any other changes in duty cycle can mean troubles.

The top and bottom corners of the waveform should be sharp and voltage transitions of the edge should be straight and vertical.

Make sure the waveform isn’t riding too high off the ground level. This could indicate a high resistance or bad ground supply to the sensor.

Although the Hall CKP sensors are generally designed to operate in temperatures up to 318 °F (150 °C), they can fail at certain temperatures (cold or hot).

Cranking test of Hall type (in dist.) crankshaft position (CKP) sensor

The amplitude, frequency, and shape should be all consistent in the waveform from pulse to pulse. The amplitude should be sufficient (usually equal to sensor supply voltage), the time between pulses repeatable (except for “sync” pulses), and

Optical CranKshaft Position (CKP) Sensor

Theory of Operation

These CKP sensors are classified as “CKP Sensors - High Resolution” in industry.

The optical CKP sensors can sense position of a rotating component even without the engine running and their pulse amplitude remains constant with variations in speed. They are not affected by electromagnetic interference (EMI). They are used to switch the ignition and/or fuel injection triggering circuits on and off.

The optical sensor consists of a rotating disk with slots in it, two fiber optic light pipes, an LED, and a phototransistor as the light sensor. An amplifier is coupled to the phototransistor to create a strong enough signal for use by other electronic devices, such as PCM or ignition module.

Frequency Modulated signal.Frequency

cycle stays constant.

should be all consistent in the

“sync” pulses), and the shapes

The phototransistor and amplifier create a digital output signal (on/off pulse).

• Symptoms

No or hard starts, stall at stops, misfires, poor fuel economy, emissions failure

• Test Procedure

1. Connect the CH A lead to the sensor output or HI and its ground lead to the sensor output LO or GND.

3. Enter the measurement setup menu, select test items, automatically the measurement setup of the project

or select measurement project; Enter

• Reference Waveform

increases with increasing engine RPM. Duty

• Troubleshooting Tips

The duty cycle of the waveform changes only when a “sync” pulse is displayed. Any other changes in duty cycle can mean troubles.

The top and bottom corners of the waveform should be sharp. However, the left upper corner may appear rounded on some of the higher frequency (high data rate) optical distributors. This is normal.

Optical CKP sensors are very susceptible to malfunction from dirt or oil interfering with the light transmission through the rotating disk. When dirt or oil enters into the sensitive areas of the sensors, no starts, stalls, or misfires can occur.

The amplitude, frequency, and shape

waveform from pulse to pulse. The amplitude should be sufficient, the time between pulses repeatable (except for

repeatable and predictable. Consistency is the key.

Magnetic Camshaft Position (CMP) Sensor

• Theory of Operation The magnetic CMP sensors are AC signal generating analog sensors. The generally consist of a wire wrapped, soft bar magnet with two connections. These two winding, or coil, connections are the sensor’s output terminals. When a ring gear (a reluctor wheel) rotates past this sensor, it induces a voltage in the winding. A uniform tooth pattern on the reluctor wheel produces a sinusoidal series of pulses having a consistent shape. The amplitude is proportional to the rotating speed of the reluctor w h ee l (that is, the crankshaft or camshaft). The frequency is based on the rotational speed of the reluctor. The air gap between the sensor’s magnetic tip and the reluctor wheel greatly affects the sensor’s signal amplitude.

They are used to determine where TDC (Top Dead Center) position is located by creating a “synchronous” pulse which is generated by either omitting teeth on the reluctor wheel or moving them closer together. The PCM or ignition module uses the CMP sensors to trigger ignition or fuel injector events. The magnetic CMP and CKP sensors are susceptible to Electromagnetic Interference (EMI or RF) from high voltage spark plug wires, car phones or other electronic devices on the vehicle. This can cause a driveability problem or set a Diagnostic Trouble Code (DTC).

•

Symptoms

Long cranking time, poor fuel economy, emissions failure

• Test Procedure

1. Connect the CH A lead to the sensor output or HI and its ground lead to the sensor output LO or GND.

2. Key On, Engine Running, let the engine idle, or use the throttle to accelerate or decelerate the

engine or drive the vehicle as needed to make the driveability, or emissions, problem occur.

3. Enter the measurement setup menu, select test items, automatically the measurement setup of the project

or select measurement project; Enter

• Reference Waveform

The amplitude and frequency increase with engine speed (RPM).

The amplitude, frequency and shape should be all consistent for the conditions (RPM, etc.), the time between pulses repeatable (except for “sync” pulses), and the shapes repeatable and predictable.

• Troubleshooting Tips

Make sure the frequency of the waveform is keeping pace with engine RPM, and that the time between pulses only changes when a “sync” pulse is displayed. This time changes only when a missing or extra tooth on the reluctor wheel passes the sensor. That is, any other changes in time between the pulses can mean trouble. Look for abnormalities observed in the waveform to coincide with an engine sputter or driveability problem.

Hall Effect Camshaft Position (CMP) Sensor

•

Theory of Operation

These CMP sensors are classified as “CMP Sensors - Low Resolution” in industry.

The Hall CMP sensors are low resolution (accuracy) digital sensors which generate the CMP signal, that is a low frequency (tens of Hz) square wave switching between zero and V Ref, from a Hall sensor.

The Hall CMP sensor, or switch, consists of an almost completely closed magnetic circuit containing a permanent magnet and pole pieces. A soft magnetic vane rotor travels through the remaining air gap between the magnet and the pole piece. The opening and closing of the vane rotor’s window interrupts the magnetic field, causing the Hall sensor to turn on the off like a switch - so some vehicle manufacturers call this sensor a Hall switch.

These sensors operate at different voltage levels depending on the vehicle manufacturers and deliver a series of pulses as the shaft rotates.

They are used to switch the ignition and/or fuel injection triggering circuits on and off.

The PCM uses the Hall CMP sensors to detect misfire.

• Symptoms

Long cranking time, poor fuel economy, emissions failure

• Test Procedure

1. Connect the CH A lead to the sensor output or HI and its ground lead to the sensor output LO or GND.

2. With Key On, Engine Running, let the engine idle, or use the throttle to accelerate or decelerate the engine or

drive the vehicle as needed to make the driveability, or emissions, problem occur.

3. Enter the measurement setup menu, select test items, automatically the measurement setup of the project

or select measurement project; E nter

increasing engine

• Reference Wa veform

Fixed Pulse Width signal. Frequency increases with RPM. Camshaft makes one rotation in between pulses.

• Troubleshooting Tips

The duty cycle of the waveform changes only when a “sync” pulse is displayed. Any other changes in duty

cycle can mean troubles.

The top and bottom corners of the waveform should be sharp and voltage transitions of the edge should be

straight and vertical.

Make sure the waveform isn’t riding too high off the ground level. This could indicate a high resistance or

bad ground supply to the sensor.

Although the Hall CMP sensors are generally designed to operate in temperatures up to 318°F (150°C), they

can fail at certain temperatures (cold or hot)

Optical Camshaft Position (CMP) Sensor

• Theory of Operation

These CMP sensors are classified as “CMP Sensors - High Resolution” in industry.

The optical CMP sensors are high resolution (accuracy) digital sensors which generate the CMP signal, that is a high frequency (hundreds of Hz to several kHz) square wave switching between zero and V Ref. The optical CMP sensors can sense position of a rotating component even without the engine running and their pulse amplitude remains constant with variations in speed. They are not affected by electromagnetic interference (EMI). They are used to switch the ignition and/or fuel injection triggering circuits on and off.

The optical sensor consists of a rotating disk with slots in it, two fiber optic light pipes, and LED, and a phototransistor as the light sensor. An amplifier is coupled to the phototransistor to create a strong enough signal for use by other electronic devices, such as PCM or ignition module. The phototransistor and amplifier create a digital output signal (on/off pulse)

• Symptoms

No or hard starts, stall at stops, misfires, poor fuel economy, emissions failure.

Test Procedure

•

1. Connect the CH A lead to the sensor output or HI and its ground lead to the sensor output LO or GND.

3. Enter the measurement setup menu, select test items, automatically the measurement setup of the project

or select measurement project; Enter

• Reference Waveform

Fixed Pulse Width signal.Frequency increases with increasing engine RPM.

The amplitude, frequency, and shape should be all consistent in the waveform from pulse to pulse. The amplitude should be sufficient, the time between pulses repeatable (except for “sync” pulses), and the shapes repeatable and predictable. Consistency is the key

• Troubleshooting Tips

The duty cycle of the waveform changes only when a “sync” pulse is displayed. Any other changes in duty cycle can mean troubles.

The top and bottom corners of the waveform should be sharp and voltage transitions of the edge should be straight and vertical.

Make sure the waveform isn’t riding too high off the ground level. This could indicate a high resistance or bad ground supply to the sensor.

Although the Hall CMP sensors are generally designed to operate in temperatures up to 318 °F (150 °C), they can fail at certain temperatures (cold or hot)

• Magnetic Vehicle Speed Sensor (VSS)

•

Theory of Operation

The vehicle speed sensors provides vehicle speed information to the PCM, the cruise control, and the speedometer. The PCM uses the data to decide when to engage the transmission torque converter clutch lockup and to control electronic transmission shift levels, cruise control, idle air bypass, engine cooling fan, and other functions.

The magnetic vehicle speed sensors are usually mounted directly on the transmissions or transaxles. They are two wire sensors and AC signal generating analog sensors. They are very susceptible to Electromagnetic Interference (EMI or RF) from other electronic devices on the vehicle.

They generally consist of a wire wrapped, soft bar magnet with two connections. These two winding, or coil, connections are the sensor’s output terminals. When a ring gear (a reluctor wheel) rotates past this sensor, it induces a voltage in the winding.

A uniform tooth pattern on the reluctor wheel produces a sinusoidal series of pulses having a consistent shape. The amplitude is proportional to the rotating speed of the reluctor wheel. The signal frequency is based on the rotational speed of the reluctor. The air gap between the sensor’s magnetic tip and the reluctor wheel greatly affects the sensor’s signal amplitude.

• Symptoms

Inaccurate speedometer, improper transmission shifting, problems affecting ABS and cruise control

• Test Procedure

1. Raise the drive wheels off the ground and place the transmission in drive.

2. Connect the CH A lead to the sensor output or HI and its ground lead to the sensor output LO or GND.

The amplitude and frequency

Speed Sensors make waveforms

very similar. Generally, the

3. Key On, Being Driven, monitor the VSS output signal at low speed while gradually increasing the speed of

the drive wheels.

4. Enter the measurement setup menu, select test items, automatically the measurement setup of the projec

or select measurement project; Enter

Reference Waveform

•

AC signal - Amplitude & Frequency increase with vehicle speed.

• Troubleshooting Tips

If the amplitude is low, look for an excessive air gap between the trigger wheel and the pickup.

If the amplitude wavers, look for a bent trigger wheel or shaft.

If one of the oscillations look distorted, look for a bent or damaged tooth on the trigger wheel.

IMPORTANT: When troubleshooting a missing VSS signal, check the fuse first. If there is no power to the buffer, there will be no square wave output. If the fuse is good, check the sensor first than a buffer mounted under the dash. If you have a sine wave coming from the sensor, but no square wave from the buffer, don’t assume the problem is in the buffer; it may not be there because of a loose connector between the sensor and the buffer.

increase with vehicle speed. Vehicle

whose shapes all look and behave

oscillations (the ups and downs in the waveform) are very symmetrical at constant speed.

to pulse. The amplitude should be

voltage), the time between pulses

Optical Vehicle Speed Sensor (VSS)

• Theory of Operation

The optical vehicle speed sensors are usually driven by a conventional cable and are found under the dash. They are digital sensors and are not affected by electromagnetic interference (EMI).

They generally consist of a rotating disk with slots in it, two fiber optic light pipes, a light emitting diode, and a phototransistor as the light sensor. An amplifier is coupled to the phototransistor to create a strong enough signal for use by other electronic devices, such as the PCM or ignition module. The phototransistor and amplifier create a digital output signal (on/off pulse).

Optical sensors are very susceptible to malfunction from dirt or oil interfering with the light transmission through the rotating disk. When dirt or oil enters into the sensitive areas of the sensors, driveability problems can occur and DTC’s can be set.

• Symptoms

Improper transmission shifting, inaccurate speedometer, problems affecting ABS and cruise control

• Test Procedure

1. Raise the drive wheels off the ground and place the transmission in drive.

2. Connect the CH A lead to the sensor output or HI and its ground lead to the sensor output LO or GND.

3. With KOBD (Key On, Being Driven), monitor the VSS output signal at low speed (about 30MPH) while

gradually increasing the speed of the drive wheels

4. Enter the measurement setup menu, select test items, automatically the measurement setup of the project

or select measurement project; Enter

• Reference Waveform

Frequency Modulated Signal. Frequency increases with vehicle

The signal frequency should increase with increasing vehicle speed, but the duty cycle should stay consistent at any speed. The amplitude, frequency, and shape should be all consistent in the waveform from pulse

sufficient (usually equal to sensor supply

repeatable and the shapes repeatable and

• Troubleshooting Tips

The top and bottom corners of the waveform should be sharp and voltage transitions of the edge should be straight and vertical.

All of the waveforms should be equal in height due to the constant supply voltage to the sensor. Make sure the waveform isn’t riding too high off the ground level. This could indicate a high resistance or bad ground supply to the sensor. (Voltage drop to ground should not exceed 400mV.)

Look for abnormalities observed in the waveform to coincide with a driveability problem or a DTC.

Analog Manifold Absolute Pressure (MAP) Sensor

•

Theory of Operation

Almost all domestic and import MAP sensors are analog types in design except Ford’s MAP sensor. Analog MAP sensors generate a variable voltage output signal that is directly proportional to the intake manifold vacuum, which is used by the PCM to determine the engine load. They are primarily three wire se n so r s an d a re su p p lie d w ith 5 V V Ref power, a ground circuit, and the signal output to the PCM.

High pressure occurs when the engine is under a heavy load, and low pressure (high intake vacuum) occurs when there is very little load. A bad MAP sensor can affect the air-fuel ratio when the engine accelerates and decelerates. It may also have some effect on ignition timing and other PCM outputs. A bad MAP sensor or its hose can trigger DTC’s for MAF, TP, or EGR sensors.

• Symptoms Low power, stall, hesitation, excessive fuel consumption, emissions failure.

• Test Procedure

1. Connect the CH A lead to the sensor output or HI and its ground lead to the sensor output LO or GND.

2. Enter the measurement setup menu, select test items, automatically the measurement setup of the project

or select measurement project; Enter

3. Shut off all accessories, start the engine and let it idle in park or neutral. After the idle has stabilized,

check the idle voltage.

4. Rev the engine from idle to Wide Open Throttle (WOT) with a moderate input speed (this should only

take about 2 seconds - don’t over rev the engine.)

Slow accel

Snap accel

Idle

5. Let engine speed drop back down to idle for about two seconds.

6. Rev the engine again to WOT (very quickly) and let it drop back to idle again.

7 . key to freeze the w avefo rm o n the d isplay for closer insp ection NOTE

It may be advantageous to put the sensor through its paces by using a handheld vacuum pump to see that it

generates the correct voltage at a specific vacuum.

• Reference Waveform

Check the manufacturer’s specifications for exact voltage range versus vacuum levels, and compare them to the readings on the display. Generally the sensor voltage should range about 1 .2 5V a t idle to just under 5V a t WOT and close to 0 V on full deceleration. High vacuum ( around 24In. Hg on full decel) produces low volt age (close to 0V), and low vacuum (around 3 In. Hg at full load) produces high voltage(close to 5V).

IMPORTANT: There are a few MAP sensors designed to do the opposite (high vacuum = high voltage). Some Chrysler MAP sensor s just stay at a fixed voltage when they fail, regardless of changes in vacuum level. Generally 4 cylinder engines make nosier waveforms because their vacuum fluctuates more between intake strokes.

• Troubleshooting Tips

Digital Manifold Absolute Pressure (MAP) Sensor

• Theory of Operation

Ford’s digital MAP sensor is found on many Ford and Lincoln Mercury vehicles from the early 1980’s to well into the 1990’ s. This sensor produce s a frequency modulated square wave whose frequency varies with the amount of intake vacuum sensed. It generates about 160Hz with no vacuum applied, and it generates about 105Hz when it is sensing around 19In. Hg at idle. Check the manufacturer’s specs for the year, make and model for exact vacuum versus frequency reference numbers. This is a three wire sensor, supplied with 5 V V Ref power, a ground circuit, and the digital signal output pulses based on the amount of vacuum it senses.

• Symptoms

Low power, stall, hesitation, excessive fuel consumption, emissions failure

• Test Procedure

1.Connect the CH A lead to the sensor output or HI and its ground lead to the sensor output LO or GND

2.Enter the measurement setup menu, select test items, automatically the measurement setup of the project

or select measurement project; Enter

3. With the Key On, Engine Off, apply different amounts of vacuum to the sensor using a handheld vacuum

pump.

4. Make sure that the amplitude, frequency and shape are all present, repeatable, and consistent. Amplitude

should be close to 5V. Frequency should vary with vacuum. Shape should stay constant (square wave).

5. Make sure the sensor produces the correct frequency for a given amount of vacuum, according to the

specification chart for the vehicle you are working on.

• Reference Waveform

Frequency decreases as vacuum increases. Look for pulses that are a full 5V in amplitude. Voltage transitions should be straight and vertical. Voltage drop to ground should not exceed 400mV. If the voltage drop is greater than 400mV, look for a bad ground at the sensor or the PCM.

• Troubleshooting Tips

A bad digital MAP sensor can produce incorrect frequencies, runted ( shortened ) pulses, unwanted spikes

and rounded off corners that could all have the effect of garbling “electronic communication”, thus causing a driveability or emissions problem

Analog Mass Air Flow (MAF) Sensor

• Theory of Operation

There are two main varieties of analog MAF sensors; Hot Wire type and Vane type. Hot wire type MAF sensors use heated-metal-foil sensing element to measure air flow entering the intake manifold. The sensing element is heated to about 170

˚F (77˚C), above the temperature of incoming air. As air flows over the sensing

element, it cools the element, causing resistance to drop. This causes a cor responding increase in current flow, which causes supply voltage to decrease. This signal is seen by the PCM as a change in voltage drop (high air flow = high voltage) and is used as an indication of air flow. The PCM uses this signal to calculate engine load, to determine the right amount of fuel to be mixed with the air, and ignition timing, EGR control, idle control, transmission shift points, etc.

Vane type MAF sensors, mainly, consist of a variable resistor (potentiometer) that tells the PCM the position of the vane air flow door. As the engine is accelerated and more air passes through the vane air flow sensor, the vane air door is pushed open by the incoming air. The angle of the vane air flow door is proportional to the volume of air passing by it. A vane type MAF sensor consists of a contact connected to the vane door which slides over a section of resistance material that is places around the pivot axis for the movable contact. The voltage at any point in the resistance material, as sensed through the movable contact, is proportional to the ang le o f th e v a n e a ir d o o r . Frequency decreases as vacuum increases. Look for pulses that are a full 5V in amplitude. Voltage transitions should be straight and vertical. Voltage drop to ground should not exceed 400mV. If the voltage drop is greater than 400mV, look for a bad ground at the sensor or the PCM.

Over swing of the door caused by snap accelerations provides information to the PCM for acceleration enrichment.[Many Toyotas are equipped with vane type MAF sensors operating opposite the above –their voltage is high when airflow is low.

• Symptoms

Hesitation, stall, low power, idle problems, excessive fuel consumption, emissions failure

• Test Procedure

1. Connect the CH A lead to the sensor output or HI and its ground lead to the sensor output LO or GND.

2. Enter the measurement setup menu, select test items, automatically the measurement setup of the project

or select measurement project; Enter

Full decel.

3.Shut off all accessories, start the engine and let it idle in park or neutral. After the idle has stabilized, check the

idle voltage.

4. Rev the engine from idle to Wide Open Throttle (WOT) with a moderate input speed (this should only take about

2 seconds –don’t over rev the engine).

5. Let engine speed drop back down to idle for about two seconds.

6. Rev the engine again to WOT (very quickly) and let it drop back to idle again.

7. to freeze the waveform on the display for closer inspection.

• Reference Waveform

Hot wire type MAF sensor voltage should range from just over 2 V at idle to just over 4V at WOT, and should dip slightly lower than idle voltage on full deceleration. Vane type MAF sensor voltage should range from about 1 V at idle to just over 4 V at WOT and not quite back to idle voltage on full deceleration. Generally, on non-Toyota varieties, high airflow makes high voltage and low airflow makes low voltage. When the sensor voltage output doesn’t follow airflow closely, the waveform will show it and the engine operation will be noticeably affected.

Snap accel

Slow accel

• Troubleshooting Tips

If overall voltage is low, be sure to check for cracked, broken, loose, or otherwise leaking intake air ducts.

IMPORTANT: 0.25V can make the difference between a good sensor and a bad one, or an engine that is blowing black smoke and one that is in perfect control of fuel mixture. However, because the sensor output voltages will vary substantially depending on vehicle engine families, in some cases, this sensor can be difficult to diagnose definitively.

before snap accel.

or the PCM.

Digital Slow MAF (Mass Air Flow) Sensor

• Theory of Operation

There are three main varieties of digital MAF sensors; Digital Slow type (output signals in the 30 to 500Hz range), Digital Fast type (output signals in the kHz range), and Karman Vortex type (which changes pulse width as well as frequency). A digital MAF sensor receives a 5V reference signal from the PCM and sends back a variable frequency signal that is proportional to the mass of air entering the engine. The output signal is a square wave, in most cases, with a full 5V in amplitude. As the airflow increases, the frequency of the signal generated increases. The PCM uses these signals to calculate fuel injector ON time and ignition timing and also determines MAF sensor deterioration by comparing the MAF signal to a calculated value based on MAP, TP, IAT, and RPM signals.

Digital Slow MAF sensors can be found on early to mid 1980’s GM vehicles, and many other engine systems. Generally, the older the MAF sensor, the slower the frequency it produces.

• Symptoms

Hesitation, stall, low power, idle problems, excessive fuel consumption, emissions failure

• Test Procedure

1. Connect the CH A lead to the sensor output or HI and its ground lead to the sensor output LO or GND.

2. Enter the measurement setup menu, select test items, automatically the measurement setup of the project

or select measurement project; Enter

3. With the Key On, Engine Running (KOER), use the throttle to accelerate and decelerate the engine. Try different

RPM ranges while spending more time in the RPM ranges that correspond to the driveability problem.

4. Make sure that the amplitude, frequency and shape are all correct, consistent, and repeatable.

5.Make sure that the sensor generates the correct frequency for a given RPM or airflow rate.

•

Idle air flow here

Reference Waveform

Frequency increases due to air flow increase from snap accel.

Frequency stays constant when airflow is constant. Frequency increases as air flow increases from snap acceleration. Look for pulses that are a full 5 V in amplitude. Voltage transitions should be straight and vertical. Voltage drop to ground should not exceed 400 mV. If greater than

look for a bad ground at the sensor

400mV,

• Troubleshooting Tips

Possible defects to watch for are runted (shortened) pulses, unwanted spikes, and rounded off corners that could all have the effect of garbling an electronic communication, causing a driveability or emissions problem. The sensor should be replaced if it has intermittent faults.

Digital Fast MAF (Mass Air Flow) Sensor

• Theory of Operation

Digital Fast type MAF sensors can be found on GM’s 3800V-6 engine with the Hitachi sensor, Lexus models,

and many others. The Hitachi sensor has a square wave output in the 10kHz range. Voltage level of square waves should be consistent and frequency should change smoothly with engine load and speed.

• Symptoms

Hesitation, stall, low power, idle problems, excessive fuel consumption, emissions failure

• Test Procedure

1. Connect the CH A lead to the sensor output or HI and its ground lead to the sensor output LO or GND；

2.. Enter the measurement setup menu, select test items, automatically the measurement setup of the project

or select measurement project; Enter

3. Make sure that the amplitude, frequency and shape are all consistent, repeatable, and accurate.

4. Make sure that the sensor generates the correct frequency for a given RPM or airflow rate.

• Reference Waveform

Frequency stays constant when air flow is constant. Frequency increases as air flow increases from snap acceleration. Look for pulses that are a full 5V in amplitude. Voltage transitions should be straight and vertical. Voltage drop to ground should not exceed 400mV. If greater than 400mV, look for a bad ground at the sensor or the PCM

NOTE

On some Digital Fast MAF sensors, such as the GM Hitachi sensor found on 3800Buick V-6s, the upper left corner

of the pulse is rounded off slightly. This is normal and doesn’t indicate a bad sensor. Troubleshooting Tips

• Troubleshooting Tips

Possible defects to watch for are runted (shortened) pulses, unwanted spikes, and rounded off corners that could all

have the effect of garbling an electronic communication, causing a driveability or emissions problem. The sensor

should be replaced if it has intermittent faults.

Digital Karman-Vortex MAF (Mass Air Flow) Sensor

• Theory of Operation

Karman-Vortex type MAF sensors are usually manufactured as part of the air cleaner assembly. They are commonly found on Mitsubishi engine systems. While most digital MAF sensors var y only their frequency with changes in airflow rate, the Karman-Vortex type’s signal varies Pulse Width as well as Frequency with changes in airflow rate. As the airflow increases, the frequency of the signal generated increases.

Karman-Vortex sensors differ from other digital MAF sensors during acceleration modes. During acceleration, not only does the sensor’s frequency output increases, but also its pulse width changes.

• Symptoms

Hesitation, stall, low power, idle problems, excessive fuel consumption, emissions failure

• Test Procedure

1.Connect the CH A lead to the sensor output HI and its ground lead to the sensor output LO or GND

2.Enter the measurement setup menu, select test items, automatically the measurement setup of the project

or select measurement project; Enter

3. With the Key On, Engine Running (KOER), use the throttle to accelerate and decelerate the engine. Try different

RPM ranges while spending more time in the RPM ranges that correspond to the driveability problem.

4. Make sure that the amplitude, frequency, shape, and pulse width are all consistent, repeatable and accurate for

any given operating mode.

5. Make sure that the sensor generates the correct and steady frequency for a given RPM or airflow rate.

• Reference Waveform

Karman Vortex MAF sensor during snap acceleration

Frequency increases as airflow rate

increases. Pulse width (duty cycle) is

modulated in acceleration modes.

Look for pulses hat are a full 5V in

amplitude. Look for the proper shape of the

waveform in terms of consistent, square

corners, and consistent vertical legs.

• Troubleshooting Tips

Possible defects to watch for are runted (shortened) pulses, unwanted spikes, and rounded off corners that could all

have the effect of garbling an electronic communication, causing a driveability or emissions problem. The sensor

should be replaced if it has intermittent faults.

Differential Pressure Feedback EGR (DPFE) Sensor

• Theory of Operation

An EGR ( Exhaust Gas Recirculation ) pressure sensor is a pressure transducer that tells the PCM the relative pressures in the exhaust stream passages and, sometimes, intake manifold. It is found on some Ford EEC IV and EEC V engine systems.

Ford calls it a PFE (Pressure Feedback EGR) sensor when the sensor outputs a signal that is proportional to the exhaust backpressure.

Ford calls it a DPFE (Differential Pressure Feedback EGR) sensor when the sensor outputs the relative difference in pressure between intake vacuum and exhaust.

These are important sensors because their signal input to the PCM is used to calculate EGR flow. A bad EGR pressure sensor can cause hesitation, engine pinging, and idle problems, among other driveability problems, and I/M emission test failures.

The EGR pressure sensor is usually a three wire sensor. One wire supplies the sensor with 5V via the PCM’s V Ref circuit, another wire provides the sensor ground, and the third wire is the sensor’s signal output to the PCM. Generally, Ford’s DPFE sensors are found on late model 4.0L Explorers and other vehicles and produce just under 1 V with no exhaust gas pressure and close to 5V with maximum exhaust gas pressure.

NOTE Ford’s PFE sensors produce 3.25V with no exhaust back pressure increasing to about 4.75V with 1.8PSI of exhaust back pressure. On properly operating vehicles the voltage won’ t ever get to 5V. PFE sensors can be found on many Taurus and Sable models

•

Symptoms

Hesitation, engine pinging, idle problems, I/M emission test failure

• Test Procedure

1. Hesitation, engine pinging, idle problems, I/M emission test failure

2.. Enter the measurement setup menu, select test items, automatically the measurement setup of the project

or select measurement project; Enter

3. Start the engine and hold throttle at 2500 RPM for 2–3 minutes until the engine is fully warmed up and the Feedback Fuel System is able to enter closed loop. (Verify this by viewing the O2 sensor signal, if necessary.)

4. Shut off A/C and all other accessories. Drive the vehicle under normal driving modes; start from dead stop, light acceleration, heavy acceleration, cruise, and deceleration.

5. Make sure that the amplitude is correct, repeatable, and present during EGR conditions. The sensor signal should be proportional to exhaust gas versus manifold vacuum pressures.

6. Make sure that all the hoses and lines to and from the intake manifold, EGR valve, and vacuum solenoid valve are intact, and routed properly, with no leaks. Make sure the EGR valve diaphragm can hold the proper amount of vacuum (check manufacturer’s specs.). Make sure that the EGR passageways in and around the engine are clear and unrestricted from internal carbon buildup.

7. to freeze the waveform on the display for closer inspection

• Reference Waveform

Engine accelerated

As soon as the engine reaches the predetermined EGR requirement conditions, the PCM will begin opening the EGR valve. The waveform should rise when the engine is accelerated. The waveform should fall when the EGR valve closes and the engine decelerates. EGR demands are especially high during accelerations. During idle and deceleration, the valve is closed

• Troubleshooting Tips

There should be no breaks, spikes to ground, or dropouts in the waveform.

3.3 ACTUATOR TESTS

Main Menu

System Menu

Automotive Test Menu

Actuator Test Menu

or select measurement project; Enter

ACTUATOR TESTS MENU Injector PFI/MFI Injector TBI Injector PNP Injector Bosch Mixture Cntl Sol EGR Cntl Sol IAC Motor IAC Solenoid Trans Shift Sol Turbo Boost Sol Diesel Glow Plug

Saturated Switch Type (MFI/PFI/SFI) Injector

• Theory of Operation

The fuel injector itself determines the height of the release spike. The injector driver (switching transistor) determines most of the waveform features. Generally an injector driver is located in the PCM that turns the injector on and off. Different Kinds (Saturated Switch type, Peak-and-Hold type, Bosch type Peak-and-Hold, and PNP type) of injector drivers create different waveforms. Knowing how to interpret injector waveforms (determining on-time, referencing Peak height , recognizing bad drivers, etc.) can be a very valuable diagnostic talent for driveability and emission repair.

Saturated switch injector drivers are used primarily on multiport fuel injection (MFI , P F I, SF I ) systems where the injectors are fired in groups or sequential ly. Deter mining the injector on- time is fairly easy . The injector on-time begins where the PCM grounds the circuit to turn it on and ends where the PCM opens the control circuit. Since the injector is a coil, when its electric field collapses from the PCM turning it off, it creates a spike. Saturated Switch type injectors have a single rising edge. The injector on-time can be used to see if the Feedback Fuel Control System is doing its job

• Symptoms

Hesitation, rough idle, intermittent stall at idle, poor fuel mileage, emissions test failure, low power on acceleration

• Test Procedure

1. Connect the CH A lead to the injector control signal from the PCM and its ground lead to the injector GND.

2. Start the engine and hold throttle at 2500RPM for 2- 3 minutes until the engine is fully warmed up and the

Feedback Fuel System enters closed loop. (Verify this by viewing the O2 sensor signal, if necessary.)

3. Enter the measurement setup menu, select test items, automatically the measurement setup of the project

or select measurement project; Enter

4. Shut off A/C and all other accessories. Put vehicle in park or neutral. Rev the engine slightly and watch for the

corresponding injector on-time increase on acceleration.

1) Induce propane into the intake and drive the mixture rich. If the system is working properly, the injector on time

will decrease.

2) Create a vacuum leak and drive the mixture lean. The injector on-time will increase.

3) Raise the engine to 2500 RPM and hold it steady. The injector on-time will modulate from slightly larger to

slightly smaller as the system controls the mixture. Generally, the injector on-time only has to change from

0.25ms to 0.5ms to drive the system through its normal full rich to full lean range.

IMPORTANT: If the injector on-time is not changing, either the system may be operating in an “open loop” idle

mode or the O2 sensor may be bad.

• Reference Waveform

PCM turns circuit on here

PCM turns circuit

• Troubleshooting Tips

Spikes during on-time or unusual high turn off spikes indicate the injector driver’s malfunction.

Peak and Hold Type (TBI) Injector

• Theory of Operation

Peak and Hold fuel injector drivers are used almost exclusively on Throttle Body Injection (TBI) systems. These drivers are only used on a few selected MFI systems like GM’s 2.3L Quad-4 engine family, Saturn 1.9L, and Isuzu

1.6L. The driver is designed to allow approximately 4A to flow through the injector coil and then reduce the current flow to a maximum of about 1A. Generally, far more current is required to open the pintle valve than to hold it open.

The PCM continues to ground the circuit (hold it at 0V) until it detects about 4A flowing through the injector coil. When the 4A “Peak” is reached. the PCM cuts back the current to a maximum of 1A, by switching in a current limiting resistor. This reduction in current causes the magnetic field to collapse partially, creati ng a voltage spike similar to an ignition coil spike, The PCM continues the “Hold” operation for the desired injector on-time, then it shuts the driver off by opening the ground circuit completely. This creates the second spike. Under acceleration the second spike move to the right, while the first remains stationary. If the engine is running extremely rich, both spikes are nearly on top of one another because the PCM is attempting to lean out the mixture by shortening injector on time as much as possible.

• Symptoms

Hesitation on throttle tip in, rough idle, intermittent stall at idle, poor fuel mileage, emissions test failure, low power on

acceleration.

• Test Procedure

1. Connect the CH A lead to the injector control signal from the PCM and its ground lead to the injector GND.

2. Enter the measurement setup menu, select test items, automatically the measurement setup of the project

or select measurement project; Enter

3. Shut off A/C and all other accessories. Put vehicle in park or neutral. Rev the engine slightly and watch for the corresponding injector on-time increase on acceleration.

1) Induce propane into the intake and drive the mixture rich. If the system is working properly, the injector on time will decrease.

2) Create a vacuum leak and drive the mixture lean. The injector on-time will increase.

3) Raise the engine to 2500 RPM and hold it steady. The injector on-time will modulate from slightly larger to slightly smaller as the system controls the mixture. Generally, the injector on-time only has to change from

0.25 ms to 0.5 ms to drive the system through its normal full rich to full lean range.

• Reference Wa veform

When the Feedback Fuel Control System controls fuel mixture properly, the injector on-time will modulate from about 1-6ms at idle to about 6-35ms under cold cranking or Wide Open Throttle (WOT) operation. The injector coil release spike(s) ranges are from 30V to 100V normally. The turn off spikes less than 30V may indicate shorted injector coil. Initial drive voltage should go close to 0V. If not, injector driver may be weak.

• Troubleshooting Tips

Spikes during on-time or unusual high turn off spikes indicate the injector driver’s malfunction. On GM and some

ISUZU dual TBI systems lots of extra oscillations or “hash” in between the peaks indicates a faulty injector driver

in the PCM

Straight line here (just below battery voltage) indicates good injector

PNP type injector

• Theory of Operation

A PNP type injector driver within the PCM has two positive legs and one negative leg. PNP drivers pulse power to an already grounded injector to turn it on. Almost all other injector drivers (NPN type) are opposite. They pulse ground to an injector that already has voltage applied. This is why the release spike is upside-down. Current flow is in the opposite direction. PNP type drivers can be found on several MFI systems; Jeep 4.0L engine families, some pre-1988 Chrysler engine families, a few Asian vehicles, and some Bosch vehicles in the early 1970s like the Volvo 264 and Mercedes V-8s.

The injector on-time begins where the PCM switches power to the circuit to turn it on. The injector on-time ends where the PCM opens the control circuit completely.

• Symptoms

Hesitation on throttle tip in, rough idle, intermittent stall at idle, poor fuel mileage, emissions test failure, low power

acceleration.

• Test Procedure

1. Connect the CH A lead to the injector control signal from the PCM and its ground lead to the injector GND.

2. Enter the measurement setup menu, select test items, automatically the measurement setup of the pro je ct

or select measurement project; Enter

3. Start the engine and hold throttle at 2500 RPM for 2-3 minutes until the engine is fully warmed up and the Feedback Fuel System enters closed loop. (Verify this by reviewing the O2sensor signal, if necessary.)

4. Shut off A/C and all other accessories. Put vehicle in park or neutral. Rev the engine slightly and watch for the corresponding injector on-time increase on acceleration.

1) Induce propane into the intake and drive the mixture rich. If the system is working properly, the injector on time will decrease.

2) Create a Vacuum leak and drive the mixture lean. The injector on-time will increase.

3) Raise the engine to 2500 RPM and hold it steady. The injector on-time will modulate from slightly larger to slightly smaller as the system control the mixture. Generally, the injector on-time only has to change from 0.25ms to 0.5ms to drive the system through its normal full rich to full lean range.

IMPORTANT: If the injector on-time is not changing, either the system may be o p er atin g in a n “ o p e n lo o p ” idle mode or the O2sensor may be bad.

• Reference Waveform

PCM turns injector off

PCM turns injector on by switching power on

NOTE

Some injector spike heights are “chopped” to between -30V to -60V by clamping diodes. There are usually

identified by the flat top on their spike(s) instead of a sharper point. In those cases, a shorted injector may not

reduce the spike height unless it is severely shorted

When the Feedback Fuel Control System controls

fuel mixture properly, the injector on-time will

modulate from about 1-6 ms at idle to about 6-35

ms under cold cranking or Wide Open Throttle

(WOT) operation.

The injector coil release spike(s) ranges are from

-30 V to -100 V normally.

• Troubleshooting Tips

Spikes during on-time or unusual large turn off spikes indicate the injector driver’s malfunction.

Bosch injector (BOSCH)

• Theory of Operation

Bosch type Peak and Hold injector drivers (within the PCM) are designed to allow about 4 A to flow through the injector coil, then reduce the flow to a maximum of 1 A by pulsing the circuit on a n d of f a t a h ig h f re q u en cy . The other type injector drivers reduce the current by using a “switch-in”resistor, but this type drivers reduce the current by pulsing the circuit on and off.

Bosch type Peak and Hold injector drivers are found on a few European models with MFI systems and some early to mid-1980s Asian vehicles with MFI systems.

• Symptoms

Hesitation on throttle tip in, rough idle, intermittent stall at idle, poor fuel mileage, emissions test failure, low power on

acceleration

• Test Procedure

1. Connect the CH A lead to the injector control signal from the PCM and its ground lead to the injector GND.

2. Start the engine and hold throttle at 2500 RPM for 2-3 minutes until the engine is fully warmed up and the

Feedback Fuel System enters closed loop. (Verify this by reviewing the O2sensor signal, if necessary.)

3. Enter the measurement setup menu, select test items, automatically the measurement setup of the project

or select measurement project; Enter

Shut off A/C and all other accessories. Put vehicle in park or neutral. Rev the engine slightly and watch for the

corresponding injector on-time increase on acceleration.

1) Induce propane into the intake and drive the mixture rich. If the system is working properly, the injector on time

will decrease.

2) Create a vacuum leak and drive the mixture lean. The injector on-time will increase.

3) Raise the engine to 2500 RPM and hold it steady. The injector on-time will modulate from slightly larger to

slightly smaller as the system control the mixture. Generally, the injector on-time only has to change from 0.25ms

to 0.5ms to drive the system through its normal full rich to full lean range.

IMPORTANT: If the injector on-time is not changing, either the system may be operating in an “open loop” idle

mode or the O2sensor may be bad.

• Reference Waveform

PCM turns

IMPORTANT :

release spike does not appear due to a spike suppression diode.

On some European vehicles like Jaguar, there may be only one release spike because the first

• Troubleshooting Tips

Spikes during on-time or unusual high turn off spikes indicate the injector driver’s malfunction.

Mixture Control Solenoid

• Theory of Operation

The mixture control signal is the most important output signal in a carbureted Feedback Fuel Control system. On a GM vehicle, this circuit pulses about 10 times per second, with each individual pulse (pulse width or on-time) varing, depending upon the fuel mixture needed at that moment.

In a GM vehicle, this circuit controls how long (per pulse) the main jet metering rods in the carburetor stay down (lean position). Most feedback carburetor systems operate in the same way –more mixture control on-time means lean mixture command. Generally, mixture control commands (from the PCM) that oscillate around duty cycles greater than 50% mean the system is commanding a lean mixture in an effort to compensate for a long term rich condition.

• Symptoms

Hesitation on throttle tip in, poor fuel economy, erratic idle, rich or lean emissions

• Test Procedure

IMPORTANT: Before performing the test procedure, the O2sensor must be tested and confirmed good.

1. Connect the CH A lead to the mixture solenoid control signal from the PCM and its ground lead to GND.

2. Enter the measurement setup menu, select test items, automatically the measurement setup of the project

or select measurement project; Enter

3. Start the engine and hold throttle at 2500 RPM for 2-3 minutes until the engine is fully warmed up and the Feedback Fuel System enters closed loop. (Verify this by viewing the O2sensor signal.)

4. Shut off A/C and all other accessories. Put vehicle in park or neutral. Adjust lean stop, air bleed, and idle mixture as per recommended service procedures for the carburetor being serviced.

turns

• Reference Waveform

PCM turns circuit on

NOTE: O2sensor must be good to test this circuit

PCM

When the main venturi metering circuits are adjusted properly (lean stop, air bleed, etc.), the mixture control signal should oscillate around 50% duty cycle normally. When the main metering and idle mixture adjustments are set correctly, the tall spike will oscillate slightly from right to left and back again, but remain very close to the middle of the two vertical drops in the waveform. The PCM is oscillating the signal right to left, based on input from the O2sensor.

• Troubleshooting Tips

If the duty cycle does not remain around 50 %, check for vacuum leaks or a poor mixture adjustment. If the

waveform oscillates around 50 % duty cycle during one operating mode (for instance, idle) but not another, then

check for vacuum leaks, misadjusted idle mixture, main metering mixture, or other non-feedback system problems

that affect mixture at different engine speeds.

EGR (Exhaust Gas Recirculation) Control Solenoid

• Theory of Operation

EGR systems are designed to dilute the air-fuel mixture and limit NOx formation when combustion temperatures generally exceed 2500°F (1371°C) and air-fuel ratios are lean. The effect of mixing exhaust gas (a relatively inert gas) with the incoming air-fuel mixture is a sort of chemical buffering or cooling of the air and fuel molecules in the combustion chamber. This prevents excessively rapid burning of the air-fuel charge, or even detonation, both of which can raise combustion temperatures above 2500°F. The initial formation of NOx is limited by EGR flow and then the catalytic converter acts to chemically reduce the amounts of produced NOx entering the atmosphere. How much and when EGR flow occurs is very important to emissions and driveability. To precisely control EGR flow, the PCM sends Pulse Width Modulated signals to a vacuum solenoid v alv e to co n tro l v a cu u m flow to the EGR valve. When applying vacuum, the EGR valve opens, allowing EGR flow. When blocking vacuum, EGR flow stops. Most engine control systems do not enable EGR operation during cranking, engine warm up, deceleration, and idling. EGR is precisely controlled during acceleration modes to optimize engine tor q u e.

• Symptoms

Hesitation, loose power, stall, emissions with excessive NOx, engine detonation (pinging)

• Test Procedure

1. Connect the CH A lead to the EGR control signal from the PCM and its ground lead to GND.

2. Start the engine and hold throttle at 2500 RPM for 2-3 minutes until the engine is fully warmed up and the

Feedback Fuel System enters closed loop. (Verify this this by viewing the O2sensor signal.)

3. Enter the measurement setup menu, select test items, automatically the measurement setup of the project

or select measurement project; Enter

4.Shut off A/C and all other accessories. Drive the vehicle under normal driving modes; start from dead stop, light

acceleration, heavy acceleration, cruise, and deceleration.

5. Make sure that the amplitude, frequency, shape, and pulse width are all correct, repeatable, and present during

EGR flow conditions.

6. Make sure that all the hoses and lines to and from the intake manifold, EGR valve, and vacuum solenoid valve

are all intact, and routed properly, with no leaks. Make sure the EGR valve diaphragm can hold the proper amount

of vacuum. Make sure that the EGR passageways in and around the engine are clear and unrestricted from internal

carbon buildup.

circuit here

circuit off

• Reference Waveform

PCM pulses

PCM turns circuit on

PCM turns

As soon as the engine reaches the predetermined EGR requirement conditions, the

PCM should begin pulsing the EGR solenoid with a pulse width modulated signal to

open the EGR solenoid valve. EGR demands are especially high during accelerations

• Troubleshooting Tips

If the waveform has runted (shortened) spike heights, it indicates a shorted EGR vacuum solenoid. If the waveform

has a flat line (no signal at all), it indicates a PCM failure, PCM’s EGR conditions not met, or wiring or connector

problem

Too much EGR flow can make the vehicle hesitate, loose power, or even stall. Not enough EGR flow can result in

emissions with excessive NOx and engine detonation (pinging).

IAC (Idle Air Control) Motor

• Theory of Operation

Idle air control valves keep the engine idling as low as possible, without stalling, and as smoothly as possible when accessories such as air conditioning compressors, alternators, and power steering load the engine.

Some IAC valves are solenoids (most Fords), some are rotating motors (European Bosch), and some are gear reduction DC stepper motors (most GM, Chrysler). In all cases, however, the PCM varies the amplitude or p u lse width of the signal to control its operation and ultimately, idle speed.

Rotating IAC motors receive a continuous pulse train. The duty cycle of the signal controls the speed of the motor, and in turn the amount of air bypassing the throttle plate.

• Symptoms

Erratic high or low idle, stalling, high activity but no change in idle.

• Test Procedure

1. Connect the CH A lead to the IAC control signal from the PCM and its ground lead to GND.

2. Enter the measurement setup menu, select test items, automatically the measurement setup of the project.

or select measurement project; Enter

3. Run the engine at idle while turning accessories (A/C, blowers, wipers, etc.) on and off. If the vehicle has an

automatic transmission, put it in and out of drive and park. This will change the load on the engine and cause the

PCM to change the output command signal to the IAC motor.

4. Make sure that idle speed responds to the changes in duty cycle.

• Reference Waveform

PCM turns circuit on

PCM turns circuit off

The idle control output command from the PCM should change when accessories are switched on and off or the transmission is switched in and out of gear. The pulse width modulated signals from the PCM should control the speed of the motor, and in turn the amount of air bypassing the throttle plate. The turn off spikes may not be present in all IAC drive circuits.

IMPORTANT: Before diagnosing IAC motor, several things must be checked and verified; the throttle plate

should be free of carbon buildup and should open and close freely, the minimum air rate (minimum throttle opening)

should be set according to manufacturer’s specifications, and check for vacuum leaks or false air leaks.

• Troubleshooting Tips

If the engine idle speed doesn’t change corresponding with the change of the PCM’s command signal, suspect a bad

IAC motor or clogged bypass passage.

IAC (Idle Air Control) Solenoid

• Theory of Operation

Idle air control solenoids keep the engine idling as low as possible, without stalling, and as smoothly as possible when accessories such as air conditioning compressors, alternators, and power steering load the engine.

Ford’s IAC solenoids are driven by a DC signal with some AC superimposed on top. The solenoid opens the throttle plate in proportion to the DC drive it receives from the PCM. The DC drive is applied by holding one end of the solenoid coil at battery positive while pulling the other end toward GND. The DC voltage at the driven pin decreases as the solenoid drive current is increased.

• Symptoms

Erratic high or low idle, stalling, high activity but no change in idle.

• Test Procedure

1. Connect the CH A lead to the IAC control signal from the PCM and its ground lead to the chassis GND.

2. Enter the measurement setup menu, select test items, automatically the measurement setup of the project

or select measurement project; Enter

3. Run the engine at idle while turning accessories (A/C, blowers, wipers, etc.) on and off. If the vehicle has an

automatic transmission, put it in and out of drive and park. This will change the load on the engine and cause the

PCM to change the output command signal to the IAC solenoid.

4. Make sure that the amplitude, frequency, and shape are all correct, repeatable, and consistent for the various idle

compensation modes.

5.Make sure that idle speed responds to the changes in the IAC drive

• Reference Waveform

The idle control output command from

the PCM should change when

accessories are switched on and off or

the transmission is switched in and out

of gear.

DC level should decrease as the IAC

solenoid drive current is increased.

IMPORTANT: Before diagnosing IAC solenoid, several things must be checked and verified; the throttle

plate should be free of carbon buildup and should open and close freely, the minimum air rate (minimum

throttle opening) should be set according to manufacturer’s specifications, and check for vacuum leaks or false air

leaks.

• Troubleshooting Tips

If the engine idle speed doesn’t change corresponding with the change of the PCM’s command signal, suspect a bad

IAC solenoid or clogged bypass passage

Transmission Shift Solenoid

• Theory of Operation

The PCM controls an automatic transmission’s electronic shift solenoid or torque converter clutch (TCC) lockup Solenoid.

The PCM opens and closes the solenoid valves using a DC switched signal. These solenoid valves, in effect, control transmission fluid flow to clutch pack, servos, torque converter lockup clutches, and o th er fu n ctio n a l co mponents of the transmission under the PCM’s control.

Some electronic shift solenoid systems use ground feed controlled solenoids that are always powered up and some systems use power feed controlled solenoids that are always grounded. A ground feed controlled solenoid on a DC switched circuit appears as a straight line at the system voltage, and drops to ground when the PCM activates the solenoid. A power feed controlled solenoid on a DC switched circuit appears as a straight line at 0 V until the PCM activates the solenoid.

Many vehicle PCM’s are programmed not to enable TCC operation until the engine reaches a certain temperature as well as a certain speed.

• Symptoms

Slow and improper shifting, engine stops running when vehicle comes to a stop

• Test Procedure

1. Connect the CH A lead to the transmission shift solenoid control signal from the PCM and its

ground lead to the chassis GND.

2. Enter the measurement setup menu, select test items, automatically the measurement setup of

the project

or select measurement project; Enter

3. Drive the vehicle as needed to make the driveability problem occur or to exercise the suspected shift solenoid circuit.

4. Make sure that the amplitude is correct for the suspected transmission operation.

5. Use the proper transmission fluid pressure gauges to make sure the transmission fluid pressure and flow being controlled by the solenoid is being effected properly by solenoid operation. This will help discriminate between an electronic problem and a mechanical problem (such as a sticking solenoid valve, clogged fluid passages, or leaking internal seals, etc.) in the transmission.

• Reference Waveform

The drive signal should be consistent and repeatable.

•

Troubleshooting Tips

If the waveform appears as a flat line (no signal at all), it can indicate a PCM failure, PCM conditions not met (shift points, TCC lockup, etc.), or wiring or connector problems.

Turbo Boost Control Solenoid

•

Theory of Operation

Turbochargers increase horsepower considerably without increasing engine piston displacement. Turbochargers

also improve torques over the useful RPM range and fuel economy, and reduces exhaust gas emissions.

Turbocharger’s boost pressure must be regulated to obtain optimum acceleration, throttle response, and engine

durability. Regulating the boost pressure is accomplished by varying the amount of exhaust gas that bypasses the

exhaust side turbine. As more exhaust gas is routed around the turbine, the less boost pressure is increased.

A door (called the waste gate) is opened and closed to regulate the amount of bypass. The waste gate is controlled

by a vacuum servo motor, which can be controlled by a vacuum solenoid valve that receives a control signal from

the PCM. When the PCM receives a signal from the MAP sensor indic atin g th at c er tain b o o s t p re ss ur e is re ac h ed ,

the PCM commands the vacuum solenoid valve to open in order to decreas e b o o st p r es su r e. The PCM opens the

solenoid valve via a pulse width modulated signal.

circuit 0ff

circuit on

• Symptoms

Poor driveability, engine damage (blown head gasket), hard stall under acceleration

• Test Procedure

1. Connect the CH A lead to the solenoid control signal from the PCM and its ground lead to the chassis GND.

2. Enter the measurement setup menu, select test items, automatically the measurement setup of the project

or select measurement project; Enter

3. Start the engine and hold throttle at 2500 RPM for 2-3 minutes until the engine is fully warmed up and the

Feedback Fuel system enters closed loop. (Verify this by viewing the O2sensor signal, if necessary.)

4. Drive the vehicle as needed to make the suspected problem occur.

5. Make sure that the drive signal comes on as the boost pressure is regulated and the wastegate actually responds to

the solenoid control signal.

• Reference Waveform

PCM turns

As soon as the turbo engine reaches a

predetermined boost pressure under

acceleration, the PCM should begin

pulsing the turbo boost solenoid with a

varying pulse width modulated signal to

open the waste gate. On deceleration, the

signal is stopped and the valve is closed.

Troubleshooting Tips

•

If the turn off spikes are not present, the solenoid coil may be shorted.

If the drive signal never appears under the high boost conditions, the driver within the PCM may have failed.

If the turn off spikes are runted (shortened), the vacuum solenoid valve may be shorted.

Diesel Glow Plug

Theory of Operation Starting cold diesel engines are not easy because Blowby past the piston rings and thermal losses reduce the amount of compression possible. Cold starting can be improved by a sheathed element glow plug in the precombustion chamber (in case of Direct-injection (DI) engines, in the m a in co mbustion chamber).

When current flows through the heating coil of the glow plug, a portion of the fuel around the glow plug’s hot tip is vaporized to assist in igniting the air-fuel mixture. Newer glow plug systems, which continue to operate after engine startup for up to 3 minutes, improve initial engine performance, reduce smokes, emissions, and combustion noises.

Usually, a glow plug control unit supplies power to the glow plug during appropriate conditions. Some newer glow plugs are designed with a heater element that changes resistance with temperature. The glow plug’s resistance increases as the heating element gets hotter by the combustion temperature’s increment after startup.

Usually, glow plug systems are power feed controlled so the waveform of the current going through its heating element appears as a straight line at 0 V until the ignition key is switched on

• Symptoms

No or hard start, emissions with excessive smokes, excessive combustion noises (knocks)

• Test Procedure

1. Set the instrument up with the current probe. (Connect the probe to the CH A.)

2. Adjust the probe to read DC Zero.

3. Enter the measurement setup menu, select test items, automatically the measurement setup of the project

or select measurement project; Enter

4. With the diesel engine stone cold, turn on the ignition key and watch for the readings.

5. Make sure that the amplitude of the current is correct and consistent for the glow plug systems under test

off

Ignition key

• Reference Waveform

Ignition key

Ignition key switched on. Current begins to flow through glow plugs.

Look for the current going through the glow plug to be at its maximum when the ignition key is switched on. Maximum current and operating current specifications maybe available from the manufacturer’s service manual. All glow plugs should draw about the same current under cold or hot conditions

• Troubleshooting Tips

If the waveform stays flat (at 0 V), suspect a faulty glow plug. If the waveform has dropouts, suspect an open

circuit in the glow plug’s heating element. An open circuit may be caused by overheat from a faulty controller,

vibration, or fatigue related malfunctions.

3.3 Ignition System Test

Main Menu

System Menu

Automotive Test Menu

IGNITION TESTS MENU

or select measurement project; Enter

IGNITION TESTS MENU PIP/SPOUT DI Primary DI Secondary DIS (El) Primary DIS (El) Secondary

How to connect and measure secondary ignition

≈

CAUTION

PIP (Profile Ignition Pickup)/SPOUT (Spark Output)

•

Theory of Operation

The most common electronic ignition system found on Ford vehicles (primarily on Ford/Lincoln/Mercury) has been dubbed TFI tor Thick Film Ignition. This system uses a Hall Switch in the TFI module, mounted on the distributor, to produce a basic s p ar k timing signal, PIP (Profile lgnition Pickup). This signal is sent to the PCM and the PCM uses this signal to monitor results and accurately 1ime the fuel injector and electronic spark 1iming output (SPOUT)signals. T he PCM sends 1he SPOUT back to the T F I module, which then fires the ignition coil p r imary circuit. The PIP signal is primarily a frequen cy modulated signal that increases and decreases its frequency with engine RPM, but il has also a pulse width modulated component because it is acted upon by the TFI module, based on information previously received via the SPOUT signal.

The SPOUT signal is a pulse width modulated signal because the PCM continually alters the SPOUT signals pulse width, which has the primary ignition dwell and ignition timing advance information encoded in it. The frequency of the SPOUT signal also increases and decreases with engine RPM because it simply mimics the frequency of the PIP signal.

Many GM/European/Asian vehicles use a similar overall ignition circuit design

The rising and falling edges of the SPOUT move in relation to PIP. The rising edge controls spark timing and the falling edge controls coil saturation (dwell).

Watching both simultaneously using this instrument will sensor inputs. For example, if the MAP sensor tails, the edges of PIP when Manifold Absolute Pressure changes.

• Symptoms

Engine stall out, misfire, slow advance timing, hesitations, no start, poor fuel economy, low power, high emissions

• Test Procedure

1. Connect the ground leads of both channel test leads to the chassis GND's. Connect the CH A to the PIP signal

and the CH B to the SPOUT signal. Use a wiring diagram for the vehicle being serviced to get the PC M pin num b er,

or color of the wire for each circuit.

2. Enter the measurement setup menu, select test items, automatically the measurement setup of the project

or select measurement project; Enter

3. Crank or start the engine.

4. With the Key On, Engine Running, let the engine idle or use the throttle to accelerate and decelerate the engine,

or drive the vehicle as needed to make the driveability problem occur.

5. Look closely to see that the frequency of both signals is keeping pace with engine RPM and that 1he pulse

width on the pulse width modulated notches of 1he signal changes when 1iming changes are required.

6. Look for abnormalities observed in the waveforms to coincide with an engine sputter or driveability problem

• Reference Waveform

• Troubleshooting Tips

If changing manifold vacuum has no effect on the rising edges of SPOUT, check for a faulty BP/MAP sensor

If PIP is absent, the engine will not start; check for a bad TFI module or other distributor problem

If SPOUT is absent, the system may be in LOS (Limited Operation Strategy) or limp-home mode. Check tor problems in the PCM or bad wiring harness connectors.

If the rising edges of PIP or SPOUT are rounded, timing will be inaccurate, although the system may not set an error code. Check for problems in the module producing each signal.

The edges must be sharp. Anything that affects ignition timing should change the position of SPOUT (upper trace) with respect to PIP (lower trace). The notches out of the top and bottom corner of PIP go away when the SPOUT connector is removed because this cuts off the TFI's ability to encode the PIP signal with the SPOUT information.

DI (Distributor lgnition) Primary

• Theory of Operation

The ignition coil primary signal is one of the top three most important diagnostic signals in powertrain management systems. This signal can be used tor diagnosing the driveability problems such as no starts, stalls at idle or while driving, misfires, hesitation, cuts out while driving, etc.

The waveform displayed from the ignition primary circuit is very useful because occurrencies in the ignition

This test can provide valuable information about the quality of combustion in each individual cylinder. The waveform is primarily used to

1. Analyze individual cylinder's dwell (coil charging time)

2. Analyze the relationship between ignition coil and secondary circuit performance (from the tiring line or

ignition).

3. Locate incorrect air-fuel ratio in individual cylinder (from the burn line).

4. Locate fouled or damaged spark plugs that cause a cylinder misfire (from the burn line)

it's sometimes advantageous to test the ignition primary when the ignition second a ry is n o t ea sily a cce ss ib le

• Symptoms

No or hard starts, stalls, misfires, hesitation, poor fuel economy

• Test Procedure

1. Connect the CH A lead to the ignition coil primary signal (driven side) and its g r o u nd lead to the chassis GND

2. Enter the measurement setup menu, select test items, automatically the measurement setup of the project

or select measurement project; Enter

3. With the Key On, Engine Running (KOER), use the throttle to accelerate and decelerate the engine or drive the

vehicle as needed to make the driveability problem or misfire occur.

4. For cranking test, set the Trigger mode to Normal

5. Make sure that the amplitude, frequency, shape and pulse width are all consistent from cylinder to cylinder.

Look for abnormalities in the section of the waveform that corresponds to specific components.

Ignition coil begins

• Reference Waveform

changing here

• Troubleshooting Tips

Look for the drop in the waveform where the ignition coil begins charging to stay relatively consistent, which

indicates consistent dwell and timing accuracy of individual cylinder.

Look for a relatively consistent height on the "arc-over" voltage or firing line. A line that is too high indicates high resistance in the ignition secondary due to an open or bad spark plug wire or a large spark gap. A line that is too short indicates lower (than normal) resistance in the ignition secondary due to to fouled, cracked, or arcing spark plug wire, etc

Look for the spark or burn voltage to remain fairly consistent. This can be an indicator of air-fuel ratio in the cylinder It the mixture is too lean, the burn voltage may be higher, and if too rich, the voltage may be lower than normal.

Look for the burn line to be fairly clean without a lot of hash (“noise"). A lot of hash can indicate an ignition misfire in the cylinder due to over-advanced ignition timing, bad injector, fouled spark plug, or other causes. Longer burn lines (over 2 ms) can indicate an abnormally rich mixture and shorter burn line (under 0.75 ms) can indicate an abnormally lean mixture.

Look for at least 2, preferably more than 3 oscillations after the burn line. This indicates a good ignition coil (and a good condenser on point-type ignitions)

The Ignition Peak voltage and Burn voltage measurements are available in this test, but they should be corrected to account for the turns ratio of the coil windings. Look closely to see that the pulse width (dwell) changes when engine load and RPM Changes.

Arc-over or ignition voltage

Spark or bum voltage

Burn line

Coil oscillations

DI (Distributor Ignition) Secondary (Conventional Single and Parade)

• Theory of Operation

Secondary ignition patterns are very useful when diagnosing ignition related malfunctions.

The secondary scope pattern is divided into three sections:

SECONDARY FIRING SECTION

The firing section consists of a firing line and a spark (or burn) line. The firing line is a vertical line that represents the voltage required to overcome the gap of the spark plug. The spark line is a semi-horizontal line that represents the voltage required to maintain current flow across the spark gap.

SECONDARY INTERMEDIATE SECTION

The intermediate section displays the remaining coil energy as it dissipates itself by oscillating between the primary and secondary side of the coil (with the points open or transistor off).

SECONDARY DWELL SECTION

The dwell section represents coil saturation, which is the period of time the points are closed or the transistor is on. The ignition (or distributor) dwell angle is the number of degrees of distributor rotation during which the points or transistor are closed (or magnetic saturation time in degrees). Normally, it takes about 10 to 15 ms for an ignition coil to develop complete magnetic saturation from primary current.

The secondary ignition test has been an effective driveability check for over three decades along with the primary ignition test. The ignition secondary waveform can be useful in detection of problems in mechanical components of engine and fuel system, as well as the ignition system components.

When the PARADE mode is selected, this instrument will present a parade of all the cylinders, starting at the left with the spark line of the number 1 cylinder. The instrument will display the pattern for each cylinder's ignition cycle in the engine's firing order. For example, if the tiring order for a given engine is 1,4,3,2, the instrument will display the ignition cycles for each cylinder as shown starting with cylinder number 1, then 4, then 3, and then 2.

Draper 64573, O20M/3C Instruction Booklet

Specifications and Main Features

Frequently Asked Questions

User Manual