Equus 3040 User Manual
Table of Contents
YOU CAN DO IT! .............................................................................. 1
SAFETY PRECAUTIONS
SAFETY FIRST! ....................................................................... 2
ABOUT THE SCAN TOOL
VEHICLES COVERED ............................................................. 3
CONTROLS AND INDICATORS .............................................. 4
DISPLAY FUNCTIONS ............................................................ 5
ONBOARD DIAGNOSTICS
COMPUTER ENGINE CONTROLS ......................................... 7
DIAGNOSTIC TROUBLE CODES (DTCs) .............................. 12
OBD2 MONITORS ................................................................... 15
PREPARATION FOR TESTING
BEFORE YOU BEGIN .............................................................. 24
VEHICLE SERVICE MANUALS ............................................... 24
USING THE SCAN TOOL
CODE RETRIEVAL PROCEDURE .......................................... 25
ERASING DIAGNOSTIC TROUBLE CODES (DTCs) ............. 30
LIVE DATA MODE
VIEWING LIVE DATA .............................................................. 32
CUSTOMIZING LIVE DATA (PIDs) ......................................... 33
ADDITIONAL FUNCTIONS
VIEWING VEHICLE INFORMATION ....................................... 35
O2 SENSOR TEST .................................................................. 37
ADJUSTMENTS AND SETTINGS ........................................... 38
GENERIC (GLOBAL) OBD2 PID LIST ............................................
WARRANTY AND SERVICING
LIMITED ONE YEAR WARRANTY .......................................... 49
SERVICE PROCEDURES ....................................................... 49
41
i OBD2
You Can Do It!
EASY TO USE - EASY TO VIEW - EASY TO DEFINE
Easy To Use . . . .
Connect the Scan Tool to the vehicle’s
test connector.
Turn the ignition key "On.” DO NOT start
the engine.
The Scan Tool will automatically link to
the vehicle’s computer.
Easy To View . . . .
The Scan Tool retrieves stored codes,
Freeze Frame data I/M Readiness status.
Codes, I/M Readiness status and Freeze
Frame data are displayed on the Scan
Tool’s display screen. System status is
indicated by LED indicators.
Easy To Define . . . .
Read code definitions from the Scan
Tool’s display
View Freeze Frame data.
View Live Data.
OBD2 1
Safety Precautions
SAFETY FIRST
SAFETY FIRST!
This manual describes common test procedures used by experienced
service technicians. Many test procedures require precautions to avoid
accidents that can result in personal injury, and/or damage to your
vehicle or test equipment. Always read your vehicle's service manual
and follow its safety precautions before and during any test or service
procedure. ALWAYS observe the following general safety precautions:
When an engine is running, it produces carbon monoxide, a
toxic and poisonous gas. To prevent serious injury or death
from carbon monoxide poisoning, operate the vehicle ONLY
in a well-ventilated area.
To protect your eyes from propelled objects as well as hot
or caustic liquids, always wear approved safety eye
protection.
When an engine is running, many parts (such as the coolant
fan, pulleys, fan belt etc.) turn at high speed. To avoid serious
injury, always be aware of moving parts. Keep a safe distance
from these parts as well as other potentially moving objects.
Engine parts become very hot when the engine is running.
To prevent severe burns, avoid contact with hot engine
parts.
Before starting an engine for testing or trouble-shooting, make
sure the parking brake is engaged. Put the transmission in
N
D
R
L
P
park (for automatic transmission) or neutral (for manual
transmission). Block the drive wheels with suitable blocks.
Connecting or disconnecting test equipment when the
ignition is ON can damage test equipment and the vehicle's
electronic components. Turn the ignition OFF before
connecting the Code Reader to or disconnecting the Code
Reader from the vehicle’s Data Link Connector (DLC).
To prevent damage to the on-board computer when taking
vehicle electrical measurements, always use a digital
multimeter with at least 10 megOhms of impedance.
The vehicle's battery produces highly flammable hydrogen
gas. To prevent an explosion, keep all sparks, heated items
and open flames away from the battery.
Don't wear loose clothing or jewelry when working on an
engine. Loose clothing can become caught in the fan,
pulleys, belts, etc. Jewelry is highly conductive, and can
cause a severe burn if it makes contact between a power
source and ground.
2 OBD2
About the Scan Tool
VEHICLES COVERED
VEHICLES COVERED
The Scan Tool is designed to work on all OBD2 compliant vehicles. All
1996 and newer vehicles (cars and light trucks) sold in the United States
are OBD2 compliant. This includes all Domestic, Asian and European
vehicles.
Some 1994 and 1995 vehicles are OBD2 compliant. To find out if a
1994 or 1995 vehicle is OBD2 compliant, check the following:
1. The Vehicle Emissions Control Information (VECI) Label. This label
is located under the hood or by the radiator of most vehicles. If the
vehicle is OBD2 compliant, the label will state “OBD II Certified.”
VEHICLE EMISSION CONTROL INFORMATION
ENGINE FAMILY EFN2.6YBT2BA
VEHICLE
MANUFACTURER
REFER TO SERVICE MANUAL FOR ADDITIONAL INFORMATION
TUNE-UP CONDITIONS: NORMAL OPERATING ENGINE TEMPERATURE,
ACCESSORIES OFF, COOLING FAN OFF, TRANSMISSION IN NEUTRAL
EXHAUST EMISSIONS STANDARDS STANDARD CATEGORY
CERTIFICATION
IN-USE
SPARK PLUG
TYPE NGK BPRE-11
GAP: 1.1MM
2. Government Regulations require that all
OBD2 compliant vehicles must have a
“common” sixteen-pin Data Link
Connector (DLC).
DISPLACEMENT 2.6L
THIS VEHICLE CONFORMS TO U.S. EPA AND STATE
OF CALIFORNIA REGULATIONS APPLICABLE TO
1999 MODEL YEAR NEW TLEV PASSENGER CARS.
CATALYST
Some 1994 and 1995 vehicles have 16-pin connectors but are not
OBD2 compliant. Only those vehicles with a Vehicle Emissions
Control Label stating “OBD II Certified” are OBD2 compliant.
TLEV
TLEV INTERMEDIATE
OBD II
CERTIFIED
OBD II
CERTIFIED
12345678
9 10111213141516
Data Link Connector (DLC) Location
The 16-pin DLC is usually
located under the instrument
panel (dash), within 12 inches
(300 mm) of center of the panel,
on the driver’s side of most
vehicles. It should be easily
accessible and visible from a
kneeling position outside the
vehicle with the door open.
LEFT CORNER
OF DASH
NEAR
CENTER
OF DASH
BEHIND
ASHTRAY
On some Asian and European vehicles the DLC is located
behind the “ashtray” (the ashtray must be removed to access it)
or on the far left corner of the dash. If the DLC cannot be
located, consult the vehicle’s service manual for the location.
OBD2 3
About the Scan Tool
CONTROLS AND INDICATORS
CONTROLS AND INDICATORS
8
5
9
6
1
2
3
7
4
Figure 1. Controls and Indicators
See Figure 1 for the locations of items 1 through 9, below.
1.
ERASE button - Erases Diagnostic Trouble Codes (DTCs) and
"Freeze Frame" data from your vehicle's computer, and resets
Monitor status.
DTC/FF button - Displays the DTC View screen and/or scrolls
2.
the display to view DTCs and Freeze Frame data when more than
one DTC is present.
DOWN button - When in MENU mode, scrolls down through the
3.
menu and submenu selection options. When LINKED to a vehicle,
scrolls down through the current display screen to display any
additional data.
4.
LD/ENTER button - When in MENU mode, confirms the
selected option or value. When linked to a vehicle, places the Scan
tool in “Live Data” mode.
4 OBD2
About the Scan Tool
DISPLAY FUNCTIONS
5.
GREEN LED - Indicates that all engine systems are running
normally (all Monitors on the vehicle are active and performing their
diagnostic testing, and no DTCs are present).
YELLOW LED - Indicates there is a possible problem. A
6.
“Pending” DTC is present and/or some of the vehicle's emission
monitors have not run their diagnostic testing.
RED LED - Indicates there is a problem in one or more of the
7.
vehicle's systems. The red LED is also used to show that DTC(s)
are present. DTCs are shown on the Scan Tool’s LCD display. In
this case, the Multifunction Indicator (“Check Engine”) lamp on the
vehicle's instrument panel will light steady on.
8. LCD Display - Displays test results, Scan Tool functions and
Monitor status information. See
details.
9. CABLE - Connects the Scan Tool to the vehicle's Data Link Connector
(DLC).
DISPLAY FUNCTIONS
DISPLAY FUNCTIONS, below, for
11
1
2
3
4
567
9
10
8
Figure 2. Display Functions
See Figure 2 for the locations of items 1 through 11, below.
1.
Vehicle icon - Indicates whether or not the Scan Tool is being
properly powered through the vehicle's Data Link Connector (DLC).
A visible icon indicates that the Scan Tool is being powered through
the vehicle's DLC connector.
Link icon - Indicates whether or not the Scan Tool is
2.
communicating (linked) with the vehicle's on-board computer. When
visible, the Scan Tool is communicating with the computer. If the
Link icon is not visible, the Scan Tool is not communicating with the
computer.
Computer icon - When this icon is visible it indicates that the
3.
Scan Tool is linked to a personal computer. Optional “PC Link”
software is available that makes it possible to upload retrieved data
to a personal computer.
OBD2 5
About the Scan Tool
DISPLAY FUNCTIONS
4. DTC Display Area - Displays the Diagnostic Trouble Code (DTC)
number and definition. Each fault is assigned a code number that is
specific to that fault.
5. MIL icon - Indicates the status of the Malfunction Indicator Lamp
(MIL). The MIL icon is visible only when a DTC has commanded the
MIL on the vehicle's dashboard to light.
6. Pending icon - Indicates the currently displayed DTC is a "Pending"
code.
7. PERMANENT icon - Indicates the currently displayed DTC is a
“Permanent” code.
8. FREEZE FRAME icon - Indicates that “Freeze Frame” data has been
stored in the vehicle’s computer for the currently displayed DTC.
9. Code Number Sequence - The Scan Tool assigns a sequence
number to each DTC that is present in the computer's memory,
starting with "01.” This helps keep track of the number of DTCs
present in the computer's memory. Code number "01" is always the
highest priority code, and the one for which "Freeze Frame" data
has been stored.
10. Code Enumerator - Indicates the total number of codes retrieved
from the vehicle’s computer.
11. Monitor icons - Indicates which Monitors are supported by the
vehicle under test, and whether or not the associated Monitor has
run its diagnostic testing (Monitor status). When a Monitor icon is
solid, it indicates that the associated Monitor has completed its
diagnostic testing. When a Monitor icon is flashing, it indicates that
the vehicle supports the associated Monitor, but the Monitor has not
yet run its diagnostic testing.
The I/M Monitor Status icons are associated with INSPECTION
and MAINTENANCE (I/M) READINESS STATUS. Some states
require that all vehicle Monitors have run and completed their
diagnostic testing before a vehicle can be tested for Emissions
(Smog Check). A maximum of fifteen Monitors are used on OBD2
systems. Not all vehicles support all fifteen Monitors. When the
Scan Tool is linked to a vehicle, only the icons for Monitors that
are supported by the vehicle under test are visible on the display.
6 OBD2
Onboard Diagnostics
COMPUTER ENGINE CONTROLS
COMPUTER ENGINE CONTROLS
The Introduction of Electronic Engine Controls
Electronic Computer Control Systems make it possible
for vehicle manufacturers to comply with the tougher
emissions and fuel efficiency standards mandated by
State and Federal Governments.
As a result of increased air pollution (smog) in large cities,
such as Los Angeles, the California Air Resources Board
(CARB) and the Environmental Protection Agency (EPA)
set new regulations and air pollution standards to deal with
the problem. To further complicate matters, the energy crisis of
the early 1970s caused a sharp increase in fuel prices over a
short period. As a result, vehicle manufacturers were not only
required to comply with the new emissions standards, they also
had to make their vehicles more fuel-efficient. Most vehicles
were required to meet a miles-per-gallon (MPG) standard set by the U.S.
Federal Government.
Precise fuel delivery and spark timing are needed to reduce vehicle
emissions. Mechanical engine controls in use at the time (such as
ignition points, mechanical spark advance and the carburetor)
responded too slowly to driving conditions to properly control fuel
delivery and spark timing. This made it difficult for vehicle manufacturers
to meet the new standards.
A new Engine Control System had to be designed and integrated with
the engine controls to meet the stricter standards. The new system had
to:
Respond instantly to supply the proper mixture of air and fuel for any
driving condition (idle, cruising, low-speed driving, high-speed
driving, etc.).
Calculate instantly the best time to “ignite” the air/fuel mixture for
maximum engine efficiency.
Perform both these tasks without affecting vehicle performance or
fuel economy.
Vehicle Computer Control Systems can perform millions of calculations
each second. This makes them an ideal substitute for the slower
mechanical engine controls. By switching from mechanical to electronic
engine controls, vehicle manufacturers are able to control fuel delivery
and spark timing more precisely. Some newer Computer Control
Systems also provide control over other vehicle functions, such as
transmission, brakes, charging, body, and suspension systems.
OBD2 7
Onboard Diagnostics
COMPUTER ENGINE CONTROLS
The Basic Engine Computer Control System
The Computer Control System consists of an on-board
computer and several related control devices (sensors,
The on-board computer is the heart of the Computer
Control System. The computer contains several programs
with preset reference values for air/fuel ratio, spark or
ignition timing, injector pulse width, engine speed, etc.
Separate values are provided for various driving conditions,
such as idle, low speed driving, high-speed driving, low load,
or high load. The preset reference values represent the ideal
air/fuel mixture, spark timing, transmission gear selection,
etc., for any driving condition. These values are programmed
by the vehicle manufacturer, and are specific to each vehicle model.
Most on-board computers are located inside the vehicle behind the dashboard,
under the passenger’s or driver’s seat, or behind the right kick panel. However,
some manufacturers may still position it in the engine compartment.
Vehicle sensors, switches, and actuators are located throughout the
engine, and are connected by electrical wiring to the on-board computer.
These devices include oxygen sensors, coolant temperature sensors,
throttle position sensors, fuel injectors, etc. Sensors and switches are
input devices. They provide signals representing current engine
operating conditions to the computer. Actuators are output devices. They
perform actions in response to commands received from the computer.
The on-board computer receives information inputs from sensors and
switches located throughout the engine. These devices monitor critical
engine conditions such as coolant temperature, engine speed, engine
load, throttle position, air/fuel ratio etc.
The computer compares the values received from these sensors with its
preset reference values, and makes corrective actions as needed so
that the sensor values always match the preset reference values for the
current driving condition. The computer makes adjustments by
commanding other devices such as the fuel injectors, idle air control,
EGR valve or Ignition Module to perform these actions.
OUTPUT DEVICES
Fuel Injectors
Idle Air Control
EGR Valve
Ignition Module
switches, and actuators).
TYPICAL COMPUTER
CONTROL SYSTEM
On-Board
Computer
INPUT DEVICES
Coolant Temperature Sensor
Throttle Position Sensor
Fuel Injectors
INPUT DEVICES
Oxygen Sensors
8 OBD2
Onboard Diagnostics
COMPUTER ENGINE CONTROLS
Vehicle operating conditions are constantly changing. The computer
continuously makes adjustments or corrections (especially to the air/fuel
mixture and spark timing) to keep all the engine systems operating
within the preset reference values.
On-Board Diagnostics - First Generation (OBD1)
With the exception of some 1994 and 1995 vehicles,
most vehicles from 1982 to 1995 are equipped with
some type of first generation On-Board Diagnostics.
Beginning in 1988, California’s Air Resources Board
(CARB), and later the Environmental Protection Agency (EPA)
required vehicle manufacturers to include a self-diagnostic
program in their on-board computers. The program would be
capable of identifying emissions-related faults in a system. The
first generation of Onboard Diagnostics came to be known as
OBD1.
OBD1 is a set of self-testing and diagnostic instructions
programmed into the vehicle’s on-board computer. The
programs are specifically designed to detect failures in the sensors,
actuators, switches and wiring of the various vehicle emissions-related
systems. If the computer detects a failure in any of these components or
systems, it lights an indicator on the dashboard to alert the driver. The
indicator lights only when an emissions-related problem is detected.
The computer also assigns a numeric code for each specific problem
that it detects, and stores these codes in its memory for later retrieval.
These codes can be retrieved from the computer’s memory with the use
of a “Code Reader” or a “Scan Tool.”
On-Board Diagnostics - Second Generation (OBD2)
In addition to performing all the
functions of the OBD1 System, the
OBD2 System has been enhanced with
new Diagnostic Programs. These
programs closely monitor the functions
The OBD2 System is
an enhancement of the
OBD1 System.
of various emissions-related components and systems (as well as other
systems) and make this information readily available (with
the proper equipment) to the technician for evaluation.
The California Air Resources Board (CARB) conducted
studies on OBD1 equipped vehicles. The information that was
gathered from these studies showed the following:
A large number of vehicles had deteriorating or degraded
emissions-related components. These components were
causing an increase in emissions.
OBD2 9
Onboard Diagnostics
COMPUTER ENGINE CONTROLS
Because OBD1 systems only detect failed components, the
degraded components were not setting codes.
Some emissions problems related to degraded components only
occur when the vehicle is being driven under a load. The emission
checks being conducted at the time were not performed under
simulated driving conditions. As a result, a significant number of
vehicles with degraded components were passing Emissions Tests.
Codes, code definitions, diagnostic connectors, communication
protocols and emissions terminology were different for each
manufacturer. This caused confusion for the technicians working on
different make and model vehicles.
To address the problems made evident by this study, CARB and the
EPA passed new laws and standardization requirements. These laws
required that vehicle manufacturers to equip their new vehicles with
devices capable of meeting all of the new emissions standards and
regulations. It was also decided that an enhanced on-board diagnostic
system, capable of addressing all of these problems, was needed. This
new system is known as “On-Board Diagnostics Generation Two
(OBD2).” The primary objective of the OBD2 system is to comply with
the latest regulations and emissions standards established by CARB
and the EPA.
The Main Objectives of the OBD2 System are:
To detect degraded and/or failed emissions-related components or
systems that could cause tailpipe emissions to exceed by 1.5 times
the Federal Test Procedure (FTP) standard.
To expand emissions-related system monitoring. This includes a set
of computer run diagnostics called Monitors. Monitors perform
diagnostics and testing to verify that all emissions-related
components and/or systems are operating correctly and within the
manufacturer’s specifications.
To use a standardized Diagnostic Link Connector (DLC) in all
vehicles. (Before OBD2, DLCs were of different shapes and sizes.)
To standardize the code numbers, code definitions and language
used to describe faults. (Before OBD2, each vehicle manufacturer
used their own code numbers, code definitions and language to
describe the same faults.)
To expand the operation of the Malfunction Indicator Lamp (MIL).
To standardize communication procedures and protocols between
the diagnostic equipment (Scan Tools, Code Readers, etc.) and the
vehicle’s on-board computer.
OBD2 Terminology
The following terms and their definitions are related to OBD2 systems.
Read and reference this list as needed to aid in the understanding of
OBD2 systems.
10 OBD2
Onboard Diagnostics
COMPUTER ENGINE CONTROLS
Powertrain Control Module (PCM) - The PCM is the OBD2
accepted term for the vehicle’s “on-board computer.” In addition
to controlling the engine management and emissions systems,
the PCM also participates in controlling the powertrain
(transmission) operation. Most PCMs also have the ability to
communicate with other computers on the vehicle (ABS, ride
control, body, etc.).
Monitor - Monitors are “diagnostic routines” programmed into the
PCM. The PCM utilizes these programs to run diagnostic tests, and
to monitor operation of the vehicle’s emissions-related components
or systems to ensure they are operating correctly and within the
vehicle’s manufacturer specifications. Currently, up to eleven
Monitors are used in OBD2 systems. Additional Monitors will be
added as the OBD2 system is further developed.
Not all vehicles support all eleven Monitors.
Enabling Criteria - Each Monitor is designed to test and monitor
the operation of a specific part of the vehicle’s emissions system
(EGR system, oxygen sensor, catalytic converter, etc.). A specific
set of “conditions” or “driving procedures” must be met before the
computer can command a Monitor to run tests on its related system.
These “conditions” are known as “Enabling Criteria.” The
requirements and procedures vary for each Monitor. Some Monitors
only require the ignition key to be turned “On” for them to run and
complete their diagnostic testing. Others may require a set of
complex procedures, such as, starting the vehicle when cold,
bringing it to operating temperature, and driving the vehicle under
specific conditions before the Monitor can run and complete its
diagnostic testing.
Monitor Has/Has Not Run - The terms “Monitor has run” or
“Monitor has not run” are used throughout this manual. “Monitor
has
run,” means the PCM has commanded a particular Monitor to
perform the required diagnostic testing on a system to ensure the
system is operating correctly (within factory specifications). The term
“Monitor has not
particular Monitor to perform diagnostic testing on its associated part
of the emissions system.
Trip - A Trip for a particular Monitor requires that the vehicle is
being driven in such a way that all the required “Enabling Criteria”
for the Monitor to run and complete its diagnostic testing are met.
The “Trip Drive Cycle” for a particular Monitor begins when the
ignition key is turned “On.” It is successfully completed when all the
“Enabling Criteria” for the Monitor to run and complete its diagnostic
testing are met by the time the ignition key is turned “Off.” Since
each of the eleven monitors is designed to run diagnostics and
testing on a different part of the engine or emissions system, the
“Trip Drive Cycle” needed for each individual Monitor to run and
complete varies.
run” means the PCM has not yet commanded a
OBD2 11
Onboard Diagnostics
DIAGNOSTIC TROUBLE CODES (DTCs)
OBD2 Drive Cycle - An OBD2 Drive Cycle is an extended set of
driving procedures that takes into consideration the various types of
driving conditions encountered in real life. These conditions may
include starting the vehicle when it is cold, driving the vehicle at a
steady speed (cruising), accelerating, etc. An OBD2 Drive Cycle
begins when the ignition key is turned “On” (when cold) and ends
when the vehicle has been driven in such a way as to have all the
“Enabling Criteria” met for all its applicable Monitors. Only those
trips that provide the Enabling Criteria for all Monitors applicable to
the vehicle to run and complete their individual diagnostic tests
qualify as an OBD2 Drive Cycle. OBD2 Drive Cycle requirements
vary from one model of vehicle to another. Vehicle manufacturers
set these procedures. Consult your vehicle’s service manual for
OBD2 Drive Cycle procedures.
Do not confuse a “Trip” Drive Cycle with an OBD2 Drive Cycle.
A “Trip” Drive Cycle provides the “Enabling Criteria” for one
specific Monitor to run and complete its diagnostic testing. An
OBD2 Drive Cycle must meet the “Enabling Criteria” for all
Monitors on a particular vehicle to run and complete their
diagnostic testing.
Warm-up Cycle - Vehicle operation after an engine off period where
engine temperature rises at least 40°F (22°C) from its temperature
before starting, and reaches at least 160°F (70°C). The PCM uses
warm-up cycles as a counter to automatically erase a specific code
and related data from its memory. When no faults related to the
original problem are detected within a specified number of warm-up
cycles, the code is erased automatically.
DIAGNOSTIC TROUBLE CODES (DTCs)
Diagnostic Trouble Codes (DTCs) are
meant to guide you to the proper
service procedure in the vehicle’s
service manual. DO NOT replace parts
based only on DTCs without first
consulting the vehicle’s service manual
for proper testing procedures for that
particular system, circuit or component.
DTCs are alphanumeric codes that are used to identify a
problem that is present in any of the systems that are
monitored by the on-board computer (PCM). Each trouble
code has an assigned message that identifies the circuit,
component or system area where the problem was found.
OBD2 diagnostic trouble codes are made up of five characters:
The 1st character is a letter. It identifies the “main system” where
the fault occurred (Body, Chassis, Powertrain, or Network).
The 2nd character is a numeric digit. It identifies the “type” of code
(Generic or Manufacturer-Specific).
Diagnostic Trouble
Codes (DTCs) are
codes that identify a
specific problem area.
12 OBD2
Onboard Diagnostics
DIAGNOSTIC TROUBLE CODES (DTCs)
Generic DTCs are codes that are used by all vehicle manufacturers. The standards for generic DTCs, as well as their
definitions, are set by the Society of Automotive Engineers (SAE).
Manufacturer-Specific DTCs are codes that are controlled by
the vehicle manufacturers. The Federal Government does not
require vehicle manufacturers to go beyond the standardized
generic DTCs in order to comply with the new OBD2 emissions
standards. However, manufacturers are free to expand beyond
the standardized codes to make their systems easier to
diagnose.
The 3rd character is a numeric digit. It identifies the specific
system or sub-system where the problem is located.
The 4th and 5th characters are numeric digits. They identify the
section of the system that is malfunctioning.
P0201 - Injector Circuit Malfunction, Cylinder 1
OBD2 DTC EXAMPLE
B
-
Body
C
-
Chassis
P
-
Powertrain
U
-
Network
-
Generic
0
-
Manufacturer Specific
1
-
Generic
2
-
Includes both Generic and Manufacturer
3
Specific Codes
Identifies the system where the
problem is located:
1
-
Fuel and Air Metering
2
-
Fuel and Air Metering (injector circuit
malfunction only)
3
-
Ignition System or Misfire
4
-
Auxiliary Emission Control System
5
-
Vehicle Speed Control and Idle Control
System
6
-
Computer Output Circuits
7
-
Transmission
8
-
Transmission
Identifies what section of the system
is malfunctioning
P 0 2 0 1
OBD2 13
Onboard Diagnostics
DIAGNOSTIC TROUBLE CODES (DTCs)
DTCs and MIL Status
When the vehicle’s on-board computer detects
a failure in an emissions-related component or
system, the computer’s internal diagnostic
program assigns a diagnostic trouble code
(DTC) that points to the system (and subsystem)
where the fault was found. The diagnostic
program saves the code in the computer’s
memory. It records a “Freeze Frame” of conditions present when the fault was found, and lights the Malfunction
Indicator Lamp (MIL). Some faults require detection for two trips in a row
before the MIL is turned on.
The “Malfunction Indicator Lamp” (MIL) is the accepted term
used to describe the lamp on the dashboard that lights to warn
the driver that an emissions-related fault has been found.
Some manufacturers may still call this lamp a “Check Engine”
or “Service Engine Soon” light.
There are two types of DTCs used for emissions-related faults: Type “A”
and Type “B.” Type “A” codes are “One-Trip” codes; Type “B” DTCs are
usually Two-Trip DTCs.
When a Type “A” DTC is found on the First Trip, the following events
take place:
The computer commands the MIL “On” when the failure is first found.
If the failure causes a severe misfire that may cause damage to the
catalytic converter, the MIL “flashes” once per second. The MIL
continues to flash as long as the condition exists. If the condition
that caused the MIL to flash is no longer present, the MIL will light
“steady” On.
A DTC is saved in the computer’s memory for later retrieval.
A “Freeze Frame” of the conditions present in the engine or emissions
system when the MIL was ordered “On” is saved in the computer’s
memory for later retrieval. This information shows fuel system status
(closed loop or open loop), engine load, coolant temperature, fuel trim
value, MAP vacuum, engine RPM and DTC priority.
When a Type “B” DTC is found on the First Trip, the following events
take place:
The computer sets a Pending DTC, but the MIL is not ordered “On.”
“Freeze Frame” data may or may not be saved at this time
depending on manufacturer. The Pending DTC is saved in the
computer’s memory for later retrieval.
If the failure is found on the second consecutive trip, the MIL is
ordered “On.” “Freeze Frame” data is saved in the computer’s
memory.
If the failure is not found on the second Trip, the Pending DTC is
erased from the computer’s memory.
The MIL will stay lit for both Type “A” and Type “B” codes until one of
the following conditions occurs:
14 OBD2
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