Buick Riviera 1996 V6 3.8L Workshop Manual

> Powertrain Management > Computers and Control Systems > Relays and Modules - Computers and Control Systems > Powertrain Control Module <--> [Engine Control Module] > Component Information > Diagrams >

Connector Views > C1 (Blue) > Pin Information > Pins 1-15 > Page 6369

Pins 56-69 Details

> Powertrain Management > Computers and Control Systems > Relays and Modules - Computers and Control Systems > Powertrain Control Module <--> [Engine Control Module] > Component Information > Diagrams >

Connector Views > C1 (Blue) > Pin Information > Pins 1-15 > Page 6370

Pins 70-80 Details

> Powertrain Management > Computers and Control Systems > Relays and Modules - Computers and Control Systems > Powertrain Control Module <--> [Engine Control Module] > Component Information > Diagrams >

Connector Views > C2 (Clear) > Harness Connector

PCM Blue C1 Connector End View

> Powertrain Management > Computers and Control Systems > Relays and Modules - Computers and Control Systems > Powertrain Control Module <--> [Engine Control Module] > Component Information > Diagrams >

Connector Views > C2 (Clear) > Pin Information > Pins 1-20

Pins 1-20 Details

> Powertrain Management > Computers and Control Systems > Relays and Modules - Computers and Control Systems > Powertrain Control Module <--> [Engine Control Module] > Component Information > Diagrams >

Connector Views > C2 (Clear) > Pin Information > Pins 1-20 > Page 6375

Pins 21-44 Details

> Powertrain Management > Computers and Control Systems > Relays and Modules - Computers and Control Systems > Powertrain Control Module <--> [Engine Control Module] > Component Information > Diagrams >

Connector Views > C2 (Clear) > Pin Information > Pins 1-20 > Page 6376

Pins 45-66 Details

> Powertrain Management > Computers and Control Systems > Relays and Modules - Computers and Control Systems > Powertrain Control Module <--> [Engine Control Module] > Component Information > Diagrams >

Connector Views > C2 (Clear) > Pin Information > Pins 1-20 > Page 6377

Pins 67-80 Details

> Powertrain Management > Computers and Control Systems > Relays and Modules - Computers and Control Systems > Powertrain Control Module <--> [Engine Control Module] > Component Information > Diagrams > Page

6378

Powertrain Control Module: Service Precautions
CONTROL MODULE SERVICE PRECAUTIONS

The control module is designed to withstand normal current draws associated with vehicle operations. Avoid overloading any circuit. When testing foropens or shorts, do not ground any of the control module circuits unless instructed. When testing for opens or shorts, do not apply voltage to any of thecontrol module circuits unless instructed. Only test these circuits with a digital voltmeter J 39200, while the control module connectors remainconnected to the control module.

USE OF CIRCUIT TESTING TOOLS

You should not use a test light to diagnose the powertrain system. You should know how to use jumper wires to test components and allow DVMreadings without damaging terminals. You should know how to use Connector Test Adapter Kit, J 35616 and use it whenever diagnostic procedurescall for front probing any connector.

ELECTROSTATIC DISCHARGE DAMAGE

CAUTION:

In order to prevent possible Electrostatic Discharge damage to the PCM, Do Not touch the connector pins or the soldered components onthe circuit board.

Electronic components used in the control systems are often designed in order to carry very low voltage. Electronic components are susceptible todamage caused by electrostatic discharge. Less than 100 volts of static electricity can cause damage to some electronic components. There are severalways for a person to become statically charged. The most common methods of charging are by friction and by induction. An example of charging byfriction is a person sliding across a car seat. Charging by induction occurs when a person with well insulated shoes stands near a highly charged objectand momentarily touches ground. Charges of the same polarity are drained off leaving the person highly charged with the opposite polarity. Staticcharges can cause damage; therefore, it is important to use care when handling and testing electronic components.

> Powertrain Management > Computers and Control Systems > Relays and Modules - Computers and Control Systems > Powertrain Control Module <--> [Engine Control Module] > Component Information > Diagrams > Page

6379

Powertrain Control Module: Description and Operation

PCM

DESCRIPTION

The Powertrain Control Module (PCM) is the control center of the vehicle. It controls the following items:

^ Fuel metering system.
^ Transaxle/transmission shifting.
^ Ignition timing.
^

On-board diagnostics for powertrain functions. It constantly looks at the information from various sensors, and controls the systems that affectvehicle performance. The PCM also performs the diagnostic function of the system. It can recognize operational problems, alert the driverthrough the MIL, and store diagnostic trouble codes which identify the problem areas to aid the technician in making repairs.

TYPE OF PCM

The type of PCM used is a PCM 32U. For service, the PCM consists of two parts: a controller (the PCM without the Knock Sensor module) and theKnock Sensor module.

> Powertrain Management > Computers and Control Systems > Relays and Modules - Computers and Control Systems > Powertrain Control Module <--> [Engine Control

Module] > Component Information > Diagrams > Page 6380

Riviera V6-3.8L VIN K (1996)

The Control Module refers to the Powertrain Control Module (PCM) or the Vehicle Control Module (VCM). The control module is designed tomaintain exhaust emission levels to Federal or California standards while providing excellent driveability and fuel efficiency. Review the componentsand wiring diagrams in order to determine which systems are controlled by each specific control module. The control module monitors numerousengine and vehicle functions. The control module controls the following operations:

^ Fuel control
^ Ignition Control (IC)
^ Knock Sensor (KS) system
^ Automatic transmission shift functions
^ Cruise Control Enable (if so equipped)
^ Generator (if so equipped)
^ Evaporative Emission (EVAP) Purge
^ A/C Clutch Control
^ Cooling Fan Control

3X REFERENCE PCM INPUT

From the ignition control module, the PCM uses this signal to calculate engine RPM and crankshaft position at engine speeds above 1200 RPM. ThePCM also uses the pulses on this circuit to initiate injector pulses. If the PCM receives no pulses on this circuit, DTC P1374 will set and the PCM willuse the 18X reference signal circuit for fuel and ignition control. The engine will continue to start and run using the 18X reference signal only.

18X REFERENCE PCM INPUT

From the ignition control module, the PCM uses this signal to calculate engine RPM and crankshaft position at engine speeds below 1200 RPM. ThePCM also uses the pulses on this circuit to initiate injector pulses. If the PCM receives no pulses on this circuit, DTC P0336 will set and the PCM willuse the 3X reference signal circuit at all times for fuel and ignition control. The engine will continue to start and run using the 3X reference signalonly.

REFERENCE LOW

This is a ground circuit for the digital RPM counter inside the PCM, but the wire is connected to engine ground only through the ignition controlmodule. Although this circuit is electrically connected to the PCM, it is not connected to ground at the PCM. The PCM compares voltage pulses onthe 18X and 3X reference input circuits to any on this circuit, ignoring pulses that appear on both. If the circuit is open, or connected to ground at thePCM, it may cause poor engine performance and possibly a MIL with no DTC set.

CAMSHAFT POSITION PCM INPUT

(SFI)

The PCM uses this signal to determine the position of the cylinder #1 piston during its power stroke. This signal is used by the PCM to calculate trueSequential Fuel Injection mode of operation. The PCM compares the number of CAM pulses to the number of 18X and 3X reference pulses. Ifthe number of 18X and 3X reference pulses occurring between CAM pulses is incorrect, or if no CAM pulses are received while the engine is running,the PCM will set DTC P0341. If the cam signal is lost while the engine is running the fuel injection system will shift to a calculated sequential fuelinjection mode based on the last cam pulse, and the engine will continue to run. The engine can be re-started and will run in the calculated sequentialmode as long as the condition is present with a 1 in 6 chance of being correct.

BYPASS SIGNAL PCM OUTPUT

The PCM either allows the ignition control module to keep the spark advance at Bypass Mode 10 degrees BTDC, or the PCM commands the ignitionmodule to allow the PCM to control the spark advance (IC Mode). The ignition control module determines correct operating mode based on thevoltage level that the PCM sends to the ignition control module on the bypass circuit. The PCM provides 5 volts on the bypass circuit if the PCM isgoing to control spark timing (IC Mode). If the PCM does not apply 5 volts to the bypass circuit, or if the ignition control module does not sense the 5volts, the ignition control module will control spark timing (Bypass Mode).

IGNITION CONTROL (IC) PCM OUTPUT

The IC output circuitry of the PCM sends out timing pulses to the ignition control module on this circuit. When in the Bypass Mode, the ignitioncontrol module grounds these pulses. When in the IC Mode, these pulses are the ignition timing pulses used by the ignition control module to energizeone of the ignition coils. Proper sequencing of the 3 ignition coils, i.e.; which coil to fire, is always the job of the ignition control module.

> Powertrain Management > Computers and Control Systems > Relays and Modules - Computers and Control Systems > Powertrain Control Module <--> [Engine Control Module] > Component Information > Testing and

Inspection > Component Tests and General Diagnostics

Powertrain Control Module: Component Tests and General Diagnostics
GENERAL INFORMATION

The approved procedure for diagnosing all powertrain control system malfunctions is included in the Strategy Based Diagnostic Flow. Thepreliminary checks and the Powertrain On-Board Diagnostic System Check must be performed to successfully diagnose and repair the powertrainsystems. To read and clear diagnostic trouble codes, use a scan tool.

CLEARING DTC's

Use a scan tool to clear diagnostic trouble codes from the PCM memory. Diagnostic trouble codes can also be cleared by turning OFF the ignition anddisconnecting the battery power from the PCM for 30 seconds, but this method will also cause all diagnostic information in the PCM memory to becleared and all the diagnostic tests will have to be re-run.

DETERMINING FAULT

Since the PCM can have a failure which may affect only one circuit, following the approved diagnostic procedures will determine which circuit has aproblem and where it is. If a diagnostic table indicates that the PCM connections or PCM is the cause of a problem and the PCM is replaced, but doesnot correct the problem, one of the following conditions may exist:

^

There is a problem with the PCM terminal connections. The diagnostic table will indicate that the PCM connections or PCM is the problem. The terminals may have to be removed from the PCM connector in order to check them properly.
^ The EEPROM program is not correct for the application.
^ Incorrect components may cause a malfunction and may or may not set a DTC.
^

Symptoms

The problem is intermittent. This means that the problem is not present at the time the system is being checked. In this case, refer to and make a careful visual and physical inspection of all suspected components and wiring associated with the affected system. See:Testing and Inspection
^

Shorted solenoid, relay coil, or harness. Solenoids and relays are turned ON and OFF by the PCM using internal electronic switches calleddrivers. Each driver is part of a group of seven called output driver modules. A shorted solenoid, relay coil, or harness will not damage thePCM but will cause the solenoid or relay to be inoperative. The J 34636 tester, or equivalent, provides a fast, accurate means of checking for ashorted coil or a short to battery voltage.

> Powertrain Management > Computers and Control Systems > Relays and Modules - Computers and Control Systems > Powertrain Control Module <--> [Engine Control Module] > Component Information > Testing and

Inspection > Page 6383

Powertrain Control Module: Service and Repair

CAUTIONS:

^

In order to prevent possible electrostatic discharge damage to the PCM, do not touch the connector pins or soldered components on the circuitboard.

^

In order to prevent internal PCM damage, leave the ignition OFF when installing or removing the PCM connectors and disconnecting orreconnecting the power to the PCM (battery cable, PCM pigtail, PCM fuse, jumper cables, etc.).

NOTES ON REPLACEMENT

Service of the PCM should normally consist of either replacement of the PCM or EEPROM programming. If the diagnostic procedures call for PCMReplacement, check the PCM first to see if it is the correct part. If the PCM is faulty, remove it and install the new service PCM.

The new service PCM will not be programmed. You must program the new PCM. DTC PO6O2 indicates the EEPROM is not programmed or hasmalfunctioned.

When replacing the production PCM with a service PCM (controller), it is important to transfer the broadcast code and production PCM number tothe service PCM label. Do not record on PCM cover. This will allow positive identification of PCM parts throughout the service life of the vehicle.

REMOVE OR DISCONNECT

1. Disconnect the negative battery cable. Refer to cautions at the top of this article.2. Remove the PCM from mounting hardware.3. Remove the harness connectors from PCM.4. Remove the PCM from instrument panel.5. If the PCM is being replaced, remove the KS module for installation in the new PCM.

INSTALL OR CONNECT

1. If a new PCM is being installed, install the KS module from the original PCM.2. Install the connectors to PCM.3. Install the PCM into vehicle.4. Connect the negative battery cable.5. If a new PCM is being installed, program the EEPROM.

EEPROM PROGRAMMING

1. Set-up - Ensure that the following conditions have been met:
^ The battery is fully charged.

^ The ignition is ON.

> Powertrain Management > Computers and Control Systems > Relays and Modules - Computers and Control Systems > Powertrain Control Module <--> [Engine Control

Module] > Component Information > Testing and Inspection > Page 6384

Riviera V6-3.8L VIN K (1996)

^ The Vehicle Interface Module cable connection at the DLC is secure.

2. Program the PCM using the latest software matching the vehicle. Refer to up-to-date Techline equipment users instructions.3. If the PCM fails to program, proceed as follows:
^ Ensure that all PCM connections are OK.

^ Check the Techline equipment for the latest software version.
^ Attempt to program the PCM. If the PCM still cannot be programmed properly, replace the PCM. You must program the replacement PCM.

FUNCTIONAL CHECK

1. Perform the On-Board Diagnostic System Check. See: Testing and Inspection2. Start the engine and the engine run for one minute.

3. Use the scan tool in order to scan for the DTCs.4. If DTC P0325 sets, the KS module is not fully seated, is missing, or is malfunctioning.

> Powertrain Management > Computers and Control Systems > Relays and Modules - Computers and Control Systems > Knock Sensor Module > Component Information > Description and Operation

Knock Sensor Module: Description and Operation
DESCRIPTION

The PCM contains a replaceable Knock Sensor (KS) module. The KS module contains the circuitry that allows the PCM to utilize the KS signal anddiagnose the KS sensors and circuitry. If the PCM is replaced, the KS module needs to be transferred from the original PCM. If the KS module ismissing or faulty causing a continuous knock condition to be indicated, the PCM will set DTC P0325.

DTCs P0325, P0326, and P0327 are designed to diagnose the KS module, the knock sensors, and related wiring, so problems encountered with the KSsystem should set a DTC.

> Powertrain Management > Computers and Control Systems > Relays and Modules - Computers and Control Systems > Knock Sensor Module > Component Information > Description and Operation > Page 6388

Knock Sensor Module: Service and Repair

PCM

Knock Sensor Control Module

Removal Procedure

(KS)

1. Remove the PCM.2. Remove the Knock Sensor Module cover.3. Gently squeeze the latches on the KS Module and carefully lift the KS Module out of the PCM.

Installation Procedure

1. Carefully insert the KS module into the socket in the PCM. Carefully press down on the KS Module until the latches engage.2. Install the KS Module cover to the PCM.3. Install the PCM.

> Powertrain Management > Computers and Control Systems > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Locations

Mass Air Flow (MAF) Sensor: Locations

LH Side Of Engine

LH Front Of Engine

> Powertrain Management > Computers and Control Systems > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams >

Diagram Information and Instructions > Abbreviation

Mass Air Flow (MAF) Sensor: Diagram Information and InstructionsAbbreviation
A/C Air Conditioning

CCM

Central Control Module

CKT

Circuit

CONN

Connector

EBCM Electronic Brake Control Module
EBTCM Electronic Brake and Traction Control Module

ECM

Engine Control Module

HARN

Harness

I/P

Instrument Panel

LH Left Hand
PCM

Powertrain Control Module

RH

Right Hand

TERM

Terminal

> Powertrain Management > Computers and Control Systems > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams >

Diagram Information and Instructions > Abbreviation > Page 6396

Body Part Names

> Powertrain Management > Computers and Control Systems > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams >

Diagram Information and Instructions > Abbreviation > Page 6397

Mass Air Flow (MAF) Sensor: Diagram Information and InstructionsCell References
CELL REFERENCES

"CELL"

General Motors vehicles often use references in their electrical wiring diagrams. These references are used in the Original EquipmentManual to refer to a section in the manual and not a specific diagram(s).

GM Sample Diagram W/ Cell Reference

For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In theexample, "Section 20" is the engine control section of the manual.

Note:

If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when theresults are displayed note the path displayed. This will show the system the component belongs in.

Diagrams / Electrical Diagrams

To navigate through these "Cell" references start at the vehicle level and go to: - for a complete list of the diagramsavailable for the vehicle. Choose the you are working on and view those diagrams. system

> Powertrain Management > Computers and Control Systems > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams >

Diagram Information and Instructions > Abbreviation > Page 6398

Mass Air Flow (MAF) Sensor: Diagram Information and InstructionsElectrostatic Discharge (ESD Sensitive Devices)

All Electrostatic Discharge sensitive components are Solid State and the following information applies to them.(ESD)

ESD Symbol

Typical Schematic

The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technicianshould follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to theelectronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible.

1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after slidingHandling Procedures

across a seat, sitting down from a standing position or walking a distance.

Measuring Procedures

The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless soinstructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or couldlead to electrostatic discharge.

2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure.3. When using a voltmeter, be sure to connect the ground lead first.4. Do not remove a part from its protective package until it is time to install the part.5. Before removing the part from its package, ground the package to a known good ground on the vehicle.

> Powertrain Management > Computers and Control Systems > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams >

Diagram Information and Instructions > Abbreviation > Page 6399

Mass Air Flow (MAF) Sensor: Diagram Information and InstructionsOn Board Diagnostics II (OBDII) Symbol

On Board Diagnostics II (OBDII) Symbol

The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation.Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit.

> Powertrain Management > Computers and Control Systems > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams >

Diagram Information and Instructions > Abbreviation > Page 6400

Mass Air Flow (MAF) Sensor: Diagram Information and InstructionsSchematic Symbols

> Powertrain Management > Computers and Control Systems > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter

/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Abbreviation > Page 6401

Riviera V6-3.8L VIN K (1996)

Fig.1-Symbols (Part 1 Of 3)

Fig.2-Symbols (Part 2 Of 3)

> Powertrain Management > Computers and Control Systems > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter

/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Abbreviation > Page 6402

Riviera V6-3.8L VIN K (1996)

Fig.3-Symbols (Part 3 Of 3)

Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, theshaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring.
Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position.

Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fullyretracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater theretraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors aregenerally larger and provide a calibrated control.

> Powertrain Management > Computers and Control Systems > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams >

Diagram Information and Instructions > Abbreviation > Page 6403

Mass Air Flow (MAF) Sensor: Diagram Information and InstructionsSupplemental Inflatable Restraint (SIR) System

SIR Symbol

The Supplemental Inflatable Restraint symbol is used on schematics to alert the technician to the following important caution.(SIR)

CAUTION: CAUTIONS

This vehicle is equipped with SIR. Refer to in SIR under Air Bags and Seat Belts before performing service on or around SIRcomponents or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR systemrepairs.

> Powertrain Management > Computers and Control Systems > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams >

Diagram Information and Instructions > Abbreviation > Page 6404

Mass Air Flow (MAF) Sensor: Diagram Information and InstructionsVehicle Zoning

Vehicle Zoning

Call Out Numbers And Zone Description

GROUND, IN-LINE CONNECTOR, PASS-THROUGH GROMMET AND SPLICE NUMBERING

All grounds, in-line connectors, pass-through grommets and splices are given identifying numbers according to where they are located in the vehicle. Theabove chart explain the numbering system.

> Powertrain Management > Computers and Control Systems > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams >

Diagram Information and Instructions > Abbreviation > Page 6405

Mass Air Flow (MAF) Sensor: Diagram Information and InstructionsWire Color Code Identification

Black: BLK
Blue:

BLU

Brown: BRN
Grey:

GR Or GRY

Green:

GRN

Natural:

NAT

Orange:

ORN

Pink:

PNK

Purple:

PPL

Red: RED
Tan:

TAN

White: WHT
Yellow:

YEL

Dark: (example: DK GRN same as Dark Green)DK
Light:

(example: LT BLU same as Light Blue)LT

> Powertrain Management > Computers and Control Systems > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams >

Diagram Information and Instructions > Abbreviation > Page 6406

Wire Size Conversion Table

> Powertrain Management > Computers and Control Systems > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams >

Diagnostic Aids > General Troubleshooting Procedures > Additional Information

Mass Air Flow (MAF) Sensor: Diagnostic AidsAdditional Information

NOTE:

Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Donot use the meter to measure resistance through a solid state module.

"ohms"

Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to then pressing the button. An audible tone will be heard whenever the meter detects continuity for at least ."PEAKMIN MAX" 1 millisecond

The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand forreference during new procedures.

> Powertrain Management > Computers and Control Systems > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams >

Diagnostic Aids > General Troubleshooting Procedures > Additional Information > Page 6410

Mass Air Flow (MAF) Sensor: Diagnostic AidsBasic Knowledge Required

(amps) (ohms)

Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures contained in this section. You should understand the basictheory of electricity and know the meaning of voltage, current and resistance . You should understand what happens in a circuit with anopen or a shorted wire. You should be able to read and understand a wiring diagram.The following four-step troubleshooting procedure is recommended:

Step 1: Check the Problem

Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you havenarrowed down the possible causes.

Step 2: Read the Electrical Schematic

Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring withthe problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try tooperate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problemcircuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty.

^Step 3: Find the fault and repair

Narrow down the possible causes.
^ Use the Troubleshooting Hints.
^ Make the necessary measurements or checks as given in the System Diagnosis.
^

Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections areOK, the most probable cause is component failure.

Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair.Step 4: Test the Repair

A customer brings in a vehicle and says that the HI beams do not work.EXAMPLE:

You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates.Step 1: Perform a System Check on the Headlight Circuit

> Powertrain Management > Computers and Control Systems > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter

/Sensor] > Component Information > Diagrams > Diagnostic Aids > General Troubleshooting Procedures > Additional Information > Page 6411

Riviera V6-3.8L VIN K (1996)

Typical Headlights Schematic

Step 2: Read the Headlights Electrical Schematic

This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why itdoesn't.

After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating thecircuit.

Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E"of C100, the TAN wires and grounds G1O5 and G109 are all good.

Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HIcontacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good.

At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that theHI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100,or a break in the LT GRN wire between C100 and the RH Headlamp.
You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself.

Step 3: Find the fault and repair it

Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble pointand make the repair.

This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working.Step 4: Check the repair by performing a System Check on the Headlights Circuit

Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neitherthe HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beamfilaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector.

> Powertrain Management > Computers and Control Systems > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams >

Diagnostic Aids > General Troubleshooting Procedures > Additional Information > Page 6412

Mass Air Flow (MAF) Sensor: Diagnostic AidsChecking Terminal Contacts

DESCRIPTION

When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors,before replacing a suspect component.

Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminalcontact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation.

Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connectoritself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion,causing an open circuit or intermittently open circuit.

> Powertrain Management > Computers and Control Systems > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter

/Sensor] > Component Information > Diagrams > Diagnostic Aids > General Troubleshooting Procedures > Additional Information > Page 6413

Riviera V6-3.8L VIN K (1996)

Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal

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Riviera V6-3.8L VIN K (1996)

Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves orrepeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminalcontact, causing an open or intermittently open circuit.

PROCEDURE

Follow the procedure below to check terminal contact.1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4.2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between

terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs ofcontamination should be replaced in its entirety: terminals, seals and connector body.

3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by

inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of

force to separate the terminals.

4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female

terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminalto the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminalin question (refer to Terminal Repair Kit, J 38125-A).

If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit.(DVM)

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Diagnostic Aids > General Troubleshooting Procedures > Additional Information > Page 6415

Mass Air Flow (MAF) Sensor: Diagnostic AidsDetecting Electrical Intermittents

PROCEDURE

Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation.

(MIN)

The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum and maximum values measured. The meter can also be set to display the average value measured.(MAX) (AVG)

When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected ofhaving an intermittent connection but is currently operating normally.1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other.

Meter Connections

This will continuously monitor the terminal contacts or length of wire being checked. Refer for examples of the variousmethods for connecting the meter to the circuit.

2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before

proceeding.

3. Press the "MIN MAX" button. The meter should read (100 millisecond record) and emit a beep. The meter is"100 ms RECORD" 1/4 second

now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX"button, which will record any voltage variations that occur for at least .1 millisecond

4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or

1/4 second.

performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the openor resistance exists. Any change in voltage will cause the meter to emit a tone for no less than (Listening for a tone whilemanipulating wiring is very helpful for narrowing down an intermittent connection.)

Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible tomonitor the meter.

To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAXrecorded voltages (unless nearly ) suggests an intermittent open or that resistance exists and should be repaired as necessary.0 volts

IMPORTANT: "100 ms RECORD"

The (100 millisecond record) mode is NOT the amount of time allowed to perform a specificprocedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode.

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Diagnostic Aids > General Troubleshooting Procedures > Additional Information > Page 6416

Mass Air Flow (MAF) Sensor: Diagnostic AidsIntermittents and Poor Connections

Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some itemsto check are:

^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out).
^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact.
^

Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the componentor mating connector.

^

Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension.Use a corresponding mating terminal to check for proper tension. Refer to for the specific procedure.Checking Terminal Contact

^

The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using theadapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tensionseems incorrect, refer to Checking Terminal Contact.

^

Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wireinsulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc.

^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle.
^

Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of amulti-strand type wire are intact, resistance could be far too HI.

To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined underthe . See: Wire Repair Procedures/Typical Electrical Repair ProceduresRepair Procedures

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Diagnostic Aids > General Troubleshooting Procedures > Additional Information > Page 6417

Mass Air Flow (MAF) Sensor: Diagnostic AidsMeter Connections

The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistancesetting to detect intermittents, it is necessary to connect the meter to the circuit.
Following are examples of the various methods of connecting the meter to the circuit to be checked:

^

Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness forcontinuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.)

^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses.
^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit.
^

If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checkingmultiple circuits quickly.

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Diagnostic Aids > General Troubleshooting Procedures > Troubleshooting Tests > Aftermarket Accessories

Mass Air Flow (MAF) Sensor: Diagnostic AidsAftermarket Accessories

Always check for aftermarket accessories as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verifythat these add-on accessories are not the cause of the problems.
Some possible causes of vehicle problems related to aftermarket accessories include:

1. Power feeds connected to points other than the Battery.2. Antenna location.3. Transceiver wiring located too close to vehicle electronic modules or wiring.4. Poor shielding or poor connectors on antenna feed line.

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Diagnostic Aids > General Troubleshooting Procedures > Troubleshooting Tests > Aftermarket Accessories > Page 6420

Mass Air Flow (MAF) Sensor: Diagnostic AidsProbing (Frontprobe & Backprobe)

(CPA)
After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance and TerminalPosition Assurance .(TPA)

Frontprobe

When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use ofproper adapters will ensure that proper terminal contact integrity is maintained. (refer to in Procedures Checking Terminal Contact).

Backprobe

Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage toconnector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by usingtoo large a test probe.

After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to . Checking Terminal Contact

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Diagnostic Aids > General Troubleshooting Procedures > Troubleshooting Tests > Aftermarket Accessories > Page 6421

Mass Air Flow (MAF) Sensor: Diagnostic AidsTesting For Voltage

Voltage Check

1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter , be sure the voltmeter's negative lead is(DVM)

connected to ground.

2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal).3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading.

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Diagnostic Aids > General Troubleshooting Procedures > Troubleshooting Tests > Aftermarket Accessories > Page 6422

Mass Air Flow (MAF) Sensor: Diagnostic AidsTesting For Continuity

Continuity Check Through A Switch

1. Remove the fuse to the circuit involved.2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test.3. Connect the other lead to the other end of the circuit.4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity.

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Diagnostic Aids > General Troubleshooting Procedures > Troubleshooting Tests > Aftermarket Accessories > Page 6423

Mass Air Flow (MAF) Sensor: Diagnostic AidsTesting For Voltage Drop

Voltage Drop Test

This test checks for voltage being lost along a wire, or through a connection or switch.

1. Connect the positive lead of a Digital Voltmeter to the end of the wire (or to one side of the connection or switch) which is closer to the(DVM)

Battery.

2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch).3. Operate the circuit.4. The DVM will show the difference in voltage between the two points.

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Mass Air Flow (MAF) Sensor: Diagnostic AidsTesting For Short to Ground

Testing For Short With Self Powered Test Light Or Ohmmeter

WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM)

1. Remove the blown fuse and disconnect the load.2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered).3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about apart) while watching the6 inches

test light or DVM.

4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point.

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Riviera V6-3.8L VIN K (1996)

Testing For Short With Test Light Or DVM

WITH A SELF-POWERED TEST LIGHT OR OHMMETER.

1. Remove the blown fuse and disconnect the Battery and load.2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side.3. Connect the other lead to a known good ground.4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about apart) while watching the6 inches

self-powered test light or ohmmeter.

5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point.

FUSES POWERING SEVERAL LOADS

"Fuse Block Details,"

1. Find the schematic under for the fuse that has blown.2. Open the first connector or switch leading from the fuse to each load.3. Replace the fuse.
^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described.

^ If fuse does not blow, refer to next step.

4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the
suspect circuit (disconnected) rather than at the fuse terminals.

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Diagnostic Aids > General Troubleshooting Procedures > Troubleshooting Tools > Test Light/Digital Voltmeter

Mass Air Flow (MAF) Sensor: Diagnostic AidsTest Light/Digital Voltmeter

12 volt

Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a light bulb with a pair of leads attached. After grounding one lead,touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point beingtested.

(DVM)

A Digital Voltmeter can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how muchvoltage is present.

(ECM)

10-megohm NEVER

An increasing number of circuits include solid state control modules. One example is the Engine Control Module . Voltages in these circuitsshould be tested only with a or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, use atest light on circuits that contain solid state components, since damage to these components may result.

When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R)connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contactsurfaces is sometimes a cause of electrical problems. Refer to in checking terminal contact. Procedures

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Diagnostic Aids > General Troubleshooting Procedures > Troubleshooting Tools > Test Light/Digital Voltmeter > Page 6428

Mass Air Flow (MAF) Sensor: Diagnostic AidsConnector Test Adapters

Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment ofprobes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals andcause incorrect measurements.

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Diagnostic Aids > General Troubleshooting Procedures > Troubleshooting Tools > Test Light/Digital Voltmeter > Page 6429

Mass Air Flow (MAF) Sensor: Diagnostic AidsSelf-Powered Test Light

A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads aretouched together, the bulb will go ON.

A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific pointsalong the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the testlight circuit will be completed and the bulb will go ON.

use a self-powered test light on circuits that contain solid state components, since damage to these components may result.NEVER

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Diagnostic Aids > General Troubleshooting Procedures > Troubleshooting Tools > Test Light/Digital Voltmeter > Page 6430

Mass Air Flow (MAF) Sensor: Diagnostic AidsOhmmeter

An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LOresistance means good continuity.

(ECM) 10-megohm

Circuits which include any solid state control modules, such as the Engine Control Module , should be tested only with a or higherimpedance digital multimeter (J 39200).

(DVM),

When measuring resistance with a Digital Voltmeter the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMsapply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading.

Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement,take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement.

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Diagnostic Aids > General Troubleshooting Procedures > Troubleshooting Tools > Test Light/Digital Voltmeter > Page 6431

Mass Air Flow (MAF) Sensor: Diagnostic AidsFused Jumper Wire

20 amp

A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire issupplied with a fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuitbeing tested.

A fused jumper may not protect solid state components from being damaged.NOTE:

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Diagnostic Aids > General Troubleshooting Procedures > Troubleshooting Tools > Test Light/Digital Voltmeter > Page 6432

Mass Air Flow (MAF) Sensor: Diagnostic AidsShort Finder

Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit andshows you the location of the short through body trim or sheet metal.