SECTION 6C1-2B - SYMPTOMS -

V6 SUPERCHARGED ENGINE

IMPORTANT:

Before performing any Service Operation or other procedure described in this Section, refer to Section 00

CAUTIONS AND NOTES in VX Service Information for correct workshop practices with regards to safety

and/or property damage.

When no diagnostic trouble codes have been set and the scan tool data values are within typical ranges, you should

diagnose the condition based on the symptoms of the complaint.

This Symptom Section starts with preliminary checks that must be performed in order to diagnose by symptom.

Then, intermittent conditions are discussed. These preliminary pages provide important information to assist you

with symptom diagnosis. Next, the contents of this Section presents the various symptoms and lists a series of

checks for each.

Many of the s ymptom diagnostic s s tar t with a very important proc edur e, a visual/physical inspec tion. Always look for

the obvious first. Some situations may warrant observing the driver. Is the driver using the correct shift lever position

or riding the brake pedal? Visually check the engine, transmission and PCM connectors. Are there any

disconnected wires or incorrectly installed components? Finally, are there obvious signs that someone may have

performed incorrect repairs? These checks take very little time; they can eliminate the time spent on a broad-base

systematic diagnos is by direc ting you to the problem . If they do not reveal the pr oblem, proceed to c heck the other

suspect systems, as shown.

The last pages of this Sec tion contain PCM connector symptom Tables. If you are diagnosing a problem , scan the

right-most column for the symptom(s) and check for the correct wire and voltage at the designated connector cavity.

PCM AND PROM

Since the PCM can have a failure which may affect only one circuit, following the Diagnostic Procedures in this

section will determine which circuit has a problem and where it is.

If a diagnostic T able indicates that the PCM connections or PCM is the cause of a problem, and the PCM is

replaced, but does not correct the problem, one of the following may be the reason:

• There is a problem with the PCM terminal connections. The diagnostic Table will say "PCM connections or

PCM." The terminals may have to be removed from the connector in order to check them properly.

• The PCM or PROM is not correct for the application. The incorrect PCM or PROM may cause a malfunction

and may or may not set a code.

• 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 the "Symptoms" Tables and make a careful physical inspection of all

components of the system involved.

• Shorted solenoid, relay coil, or harness. Solenoids and relays are turned "ON" and "OFF" by the PCM, using

internal electronic switches called "Drivers." Each "driver" is part of a group of four (called "Quad drivers").

Failure of one driver m ay c ause other drivers in the set to m alfunction. Solenoid and relay coil resis tance must

measure more than 20 ohms, in most cases. Less resistance may cause early failure of the PCM "driver."

Before replacing an PCM, be sure to check the coil resistance of all solenoids and relays controlled by the

PCM. See PCM wiring diagram for the solenoid(s) and relay(s) and the coil terminal identification.

• The PROM may be faulty. Although these rarely fail, they operate as part of the PCM. Therefore, it could be the

cause of the problem. Substitute a known good PROM.

• The replacement PCM may be faulty. After the PCM is replaced, the system should be rechecked for proper

operation. If the diagnostic Table again indicates the PCM is the problem, substitute a known good PCM.

Although this is an extremely rare condition, it could happen.

Figure 6C1-2B-1 Supercharged Engine Powertrain Wiring Harness to Engine Assembly Earth Location

1. Engine Earth Terminal.

2. Nut.

3. Engine Earth Terminal.

4. Bolt.

4288

IMPORTANT P RELIMINARY CHECKS

BEFORE USING THIS SECTION

Before using this Symptoms Section you should have performed the "On Board Diagnostic System Check" as

detailed in Section 6C1-2A of the VX Series Service Information and determined that:

1. The PCM and "Check Powertrain" lamp are operating correctly.

2. There are no diagnostic trouble codes stored.

3. There is a diagnostic trouble code stored in the PCM memory and the "Check Powertrain Lamp is not "ON."

4. The diagnostic Table for the diagnostic trouble code indicates that the trouble is intermittent.

5. Figure 6C1-2B-1 and 6C1-2B-2 on the previous page illustrates the Powertrain wiring harness to engine

assembly earth locations as described in the various "SYMPTOM TABLES" in this Section. You should become

familiar with these locations.

SYMPTOM

Verify the customer complaint, and locate the correct symptom in the table of contents. Check all the items

indicated under that symptom.

If the ENGINE CRANKS BUT WILL NOT RUN, refer to T able A 3.1-1 in Section 6C1-2A of the VX Series Service

Information.

VISUAL/PHYSICAL CHECK

Several of the symptom procedur es call f or a Caref ul Visual/Physical Check . T he im portance of this s tep cannot be

stressed too strongly it can lead to correcting a problem without further checks and can save valuable time. This

check should include:

• Check service records for any recent repairs that may indicate a related problem, or the current need for

scheduled maintenance.

• PCM sensors for being in their proper location.

• PCM earth circuits term inate at 2 separ ate eyelet terminals. O n a V6 these attach to the engine at two separate

locations: the rear of the left cylinder head, and on the by-pass tube and drive belt tensioner attaching stud,

below the generator (ref er figure at the beginning of this Sec tion) . They must be clean and tight. Check for earth

terminals that may be loose under the retaining nuts/bolts, or for terminals that may have been left off after

engine repair. Any repair of the wire to terminal connection must include soldering with rosin core solder.

(NEVER use acid core solder for any wi ring repairs.)

• Vacuum hoses for splits, kinks, and proper connections. Check thoroughly for any type of leak or restriction.

• Air leaks at throttle body mounting area and inlet manifold sealing surfaces.

• Ignition wires for cracking, hardness, proper routing and carbon tracking.

• Wiring for proper connections, pinches and cuts.

• Check for any non genuine Holden's options or accessories that may have been fitted to the vehicle that may

cause or exaggerate the problem.

INTERMITTENTS

Definition: Problem may or may not turn "ON" the "Check Powertrain" lamp or store a DTC. DO NOT use the

diagnostic code Tables for intermittent problems. W hen using the code Tables the fault must be present to locate

the problem. If a fault is intermittent, use of diagnostic trouble code Tables may result in replacement of good parts.

• Most inter mittent problem s are caused by faulty electrical connections or wiring. Perform car eful visual/physical

check as described at the start of this Section - "IMPORTANT PRELIMINARY CHECKS".

Check for:

- Poor mating of the connector halves or terminal not fully seated in the connector body (backed out).

- Improperly formed or damaged terminal. All connector terminals in the problem circuit should be carefully

reformed or replaced to insure proper contact tension.

- Poor terminal to wire connection. This requires removing the terminal from the connector body to check as

outlined in service operations.

- PCM earth circuit terminals being loose at the engine. On a V6 engine these attach to the engine at two

separate locations : the rear of the lef t cylinder head, and on the by-pass tube and drive belt tensioner attaching

stud, below the generator, refer figure at the beginning of this Section.

• If a visual/physical check does not find the cause of the problem, the car can be driven with a voltmeter

connected to a suspected circuit. A scan tool can also be used to help detect intermittent conditions. An

abnorm al voltage, or sc an tool r eading, when the problem occur s , indicates the problem m ay be in that circuit. If

the wiring and connectors check OK, and a diagnostic trouble code was stored for a circuit having a sensor,

except for DTC's 44 or 64 and 45 or 65, substitute a known good sensor and recheck.

• Loss of diagnostic code memory. To check, disconnect TP sensor and idle engine until "Check Powertrain"

lamp c omes "O N." DTC 22 should be s tored, and kept in me mory when ignition is turned "OFF." If not, the PCM

is faulty.

• An intermittent "Check Powertrain" lamp with no stored diagnostic trouble code may on V6 be caused by:

- Ignition coil shorted to earth and arcing at spark plug wires or plugs.

- Intermittent short to + 12 volts on 0-5 volt input CKTs 451 (diagnostic request), 410 (ECT sensor), 792

(MAF sensor), 417 (TP sensor), and 472 (IAT sensor).

• Check for an electrical system interference caused by a defective relay, PCM driven solenoid, or switch. They

can cause a sharp electrical surge. Normally, the problem will occur when the faulty component is operated.

• Check for improper installation of non-factory installed electrical options such as lights, 2 way radios, etc.

• EST wires should be routed away from spark plug wires, ignition wires, ignition module assembly and

generator. Wire from PCM to ignition should have a good connection.

• Check for open diode across A/C compressor clutch, and for other open diodes (refer to wiring diagrams and

TABLE A-11.1 or TABLE A-11.3 facing page wiring diagrams in Section 6C1-2A of the VX Series Service

Information).

• If problem has not been found, refer to the proper symptom and perform all checks listed there.

HARD START

Definition: Engine crank s OK, but does not s tart for a long tim e. Does eventually run, or m ay start but imm ediately

dies.

PRELIMINARY CHECKS

• Perform the careful visual/physical checks as described at the start of this Section -

"IMPORTANT PRELIMINARY CHECKS".

• Make sure the driver is using the correct starting procedure. Do not depress accelerator pedal during cranking.

• TABLE A-3.1-1 for Supercharged Engine "ENGINE CRANKS BUT WILL NOT RUN" in Section 6C1-2A of the

VX Series Service Information. Although this Table may not exactly describe the problem, most all of the

causes of a "no start" can also cause a "hard start".

• Tim e or kilometers since norm al engine tune-up has been perform ed, refer to tim e/distance intervals specified

in the Owner's Manual.

• PCM earth circuit terminals being loose at the engine. On a V6 engine these attach to the engine at two

separate locations : the rear of the lef t cylinder head, and on the by-pass tube and drive belt tensioner attaching

stud, below the

generator, refer figure at the beginning of this Section.

SENSORS

• CHECK: Engine Coolant Temperature (ECT) sensor using a scan tool, compare coolant temperature with

ambient temperature on cold engine.

- If coolant tem perature readings is 5 degrees greater than or less than am bient air temperature on a

cold engine, check resistance in coolant sensor circuit or sensor itself. Compare ECT resistance

value to the "Diagnostic Aids" Table on DTC 15 Table in Section 6C1-2A of the VX Series Service

Information.

• CHECK: MAF sens or. for a shif ted sensor, refer TABLE A-6.1 "M AF OUT PUT CHECK" in Section 6C1-2A of

the VX Series Service Information.

• CHECK: TP Sensor for binding or a high TP sensor voltage with the throttle closed.

IGNITION SYSTEM

• CHECK: Spark plug leads being misrouted at the coils or at the spark plugs.

• CHECK: For proper ignition voltage output with spark tester ST-125 or 7230.

• CHECK: Spark plugs. Remove spark plugs, check for wet plugs, cracks, wear, improper gap, burned

electrodes, or heavy deposits. Repair or replace as necessary.

• CHECK: Bare or shorted wires.

FUEL SYSTEM

• CHECK: Fuel pump relay operation pump should turn "ON" for 2 seconds when ignition is turned "ON." Use

TABLE A-4.1-1 for Supercharged Engine.

• CHECK: Fuel pressure, refer to TABLE A-4.3 in Section 6C1-2A of the VX Series Service Information.

• CHECK: Contaminated fuel or incorrect fuel.

• CHECK: If the problem occurs worse with hotter temperatures, check for leaking injectors, refer

TABLE A-4.3 in Section 6C1-2A of the VX Series Service Information.

• NOTE: A faulty in-tank fuel pump check valve will allow the fuel in the lines to drain back to the tank after

engine is stopped. To check for this condition, perform fuel system diagnosis, refer

TABLE A- 4.3 in Section 6C1-2A of the VX Series Service Information.

ADDITIONAL CHECKS

• CHECK: Exhaust bac k pres sur e, ref er T ABLE A-13 "REST RICTED EXHAUST CHECK" in Section 6C1-2A of

the VX Series Service Information.

• CHECK: IAC Operation, refer to TABLE A-7.1 in Section 6C1-2A of the VX Series Service Information.

• CHECK: Basic engine pr oblem. Camshaf t timing chain f or being str ipped or slipped, causing valve timing to be

retarded.

• CHECK: Compression. Disconnect fuse F31 before performing test.

• CHECK: Service Bulletins for updates.

SURGES AND/OR CHUGGLES

Definition: Engine power variation under steady throttle or cruise, f eels like the vehic le speeds up and slows down

with no change in the acceleration pedal.

PRELIMINARY CHECKS

• Perform the careful visual checks as described at the start of this Section -

"IMPORTANT PRELIMINARY CHECKS".

• Make sure driver understands transmission torque converter clutch, and A/C compressor operation as

explained in the Owner’s Manual.

• Tim e or k ilometer s since norm al engine tune-up has been perform ed. Refer to time/dis tance intervals specif ied

in the Owner’s Manual.

SENSORS

• CHECK: Oxygen Sensor (O2S). The Oxygen Sensor (O2S) should respond quickly to different throttle

position, if it does not, check the Ox ygen Sensor ( O2S) for silicon or other contamination’s from fuel, or use

of improper RTV sealant.

The sensor may have a white, powdery coating and result in a high but false signal voltage (rich exhaust

indication). The PCM will then reduce the amount of fuel delivered to the engine, causing a severe driveability

problem. Also, watch for green glycol contamination or cracking.

• CHECK: MAF sensor for proper operation, refer TABLE A-6.1 “M AF OUTPUT CHECK” in Section 6C1-2A

of the VX Series Service Information.

IGNITION SYSTEM

• CHECK: For proper ignition voltage output using spark tester ST-125 or 7230.

• CHECK: Spark plugs. Remove spark plugs, check for wet plugs, cracks, wear, improper gap, burned

electrodes, or heavy deposits. Repair or replace as necessary. Also, check spark plug wires.

• CHECK: Ignition secondary coil or wiring shorting to earth.

FUEL SYSTEM

• CHECK: Contaminated or incorrect fuel.

NOTE To determine if the condition is caused by a rich or lean system, the car should be driven at the

speed of the complaint. Monitoring block learn and integrator will help identify a problem.

- Lean - Long Term Fuel Trim near +25%. Refer to "Diagnostic Aids" on facing page of DTC 44 or

DTC 64 in Section 6C1-2A of the VX Series Service Information.

- Rich - Long Term Fuel Trim near - 22%. Refer to "Diagnostic Aids" on facing page of DTC 45 or

DTC 65 in Section 6C1-2A of the VX Series Service Information.

• CHECK: Fuel pressure while condition exists, refer TABLE A-4.3 in Section 6C1-2A of the VX Series

Service Information.

• CHECK: In line fuel filter. Replace if dirty or plugged.

• CHECK: Restricted fuel injectors.

ADDITIONAL CHECKS

• CHECK: PCM earth circuits for being clean, tight and in their proper location.

• CHECK: Vacuum lines for splits, kinks, leaks and proper connections.

• CHECK: Generator output voltage. Repair if less than 9 or more than 16 volts.

• CHECK: Speedometer reading with the speed on a scan tool are equal.

• CHECK: Service Bulletins for updates.

• CHECK: Correct PROM being installed into the PCM.

• CHECK: Excessive exhaust back pressure, refer TABLE A-13 "RESTRICTED EXHAUST CHECK" in

Section 6C1-2A of the VX Series Service Information.

• CHECK: TCC operation for proper operation.

LACK OF POWER, SLUGGISH, OR SPONGY

Definition: Engine delivers less than expected power. Little or no increase in speed when accelerator pedal is

pushed down part way.

PRELIMINARY CHECKS

• Perform the careful visual/physical checks as described at the start of this Section -

"IMPORTANT PRELIMINARY CHECKS".

• Compare customer's car to similar unit. Make sure the customer has an actual problem.

• Remove air filter and check air filter for dirt, or for being plugged. Replace as necessary .

• Time or kilometers since normal engine tune-up has been performed. Refer to time/distance intervals in

owner’s handbook.

SENSORS

• CHECK: MAF sens or for pr oper operation, refer TABLE A-6.1 "M AF OUT PUT CHECK" in Section 6C1-2A of

the VX Series Service Information.

ENGINE MECHANICAL

• CHECK: Engine valve timing.

• CHECK: Engine for correct or worn camshaft.

• CHECK: Compression. Disconnect the fuse F31 before performing test.

CHECK: Check Supercharger system. Refer to functional check TABLE 2-6 for

"Boost Control System Check" in Section 6C1-2C of the VX Series Service Information.

IGNITION SYSTEM

• CHECK: Secondary voltage using a shop oscilloscope or a spark tester ST-125 or 7230.

• CHECK: For ignition misfire under heavy engine load. Check eac h s park plug lead for excessive resis tance (or

open circuit), or for faulty or cracked spark plugs.

FUEL SYSTEM

• CHECK: Restricted fuel filter, refer TABLE A-4.3 in Section 6C1-2A of the VX Series Service Information.

• CHECK: Fuel pressure, refer TABL E A-4.3 in Section 6C1-2A of the VX Series Service Information.

• CHECK: Contaminated fuel, refer TABLE A-4 .3 in Section 6C1-2A of the VX Series Service Information.

• CHECK: Fuel Pump Control Module c heck . Ref er to T ABL E 4.1-1 in Section 6C1- 2A of the VX Series Service

Information.

ADDITIONAL CHECKS

• CHECK: PCM earth circuit for being clean, tight and in their proper locations.

• CHECK: Generator output voltage. Repair if less than 9 or more than 16 volts.

• CHECK: Exhaust system for possible restriction, refer TABLE A-13 in Section 6C1-2A of the VX Series

Service Information.

- Inspect exhaust system for damaged or collapsed pipes.

- Inspect muffler for heat distress or possible internal failure.

• CHECK: Torque Converter Clutch (TCC) for proper operation.

DETONATION/SPARK KNOCK

Definition: A mild to severe ping, usually worse under acceleration. The engine m akes sharp metallic knocks that

change with throttle opening.

PRELIMINARY CHECKS

Perform the careful visual/physical checks as described at the start of this Section -

"IMPORTANT PRELIMINARY CHECKS".

NOTE: If scan tool readings are normal (refer facing page of "On-Board Diagnostic System Check" in Section

6C1-2A of the VX Series Service Information) and there are no engine mechanical faults, fill fuel tank with a

premium unleaded fuel and reevaluate vehicle performance.

IGNITION SYSTEM

• CHECK: Spark plugs for proper heat range.

ENGINE MECHANICAL

• CHECK: Combustion chambers for excessive carbon build up. Remove carbon with top engine cleaner and

follow instructions on can. If the problem recurs and top engine cleaner corrects it again, look for

possible causes of high oil consumption.

• CHECK: For excessive oil in the combustion chamber.

- Valve oil seals for leaking.

• CHECK: Combustion chamber pressure by performing a compression test. Disconnect the fuse F31 before

performing test.

• CHECK: For incorrect basic engine parts such as camshaft, heads, pistons, etc.

COOLING SYSTEM

Check for obvious overheating problems:

- Low engine coolant.

- Defective engine thermostat.

- Loose water pump belt.

- Restricted air flow to radiator, or restricted water flow through radiator.

- Inoperative electric cooling f an cir cuit, refer to TABLE A-12.1 in Section 6C1-2A of the VX Series Service

Information.

- Correct coolant solution should be a 50/50 mix of antifreeze coolant and water.

FUEL SYSTEM

• CHECK: Fuel quality and proper octane rating.

• NOTE:· To determine if the condition is caused by a rich or lean system, the car should be driven at the

speed of the complaint. Monitoring block learn will help identify the problem.

- Lean - Long Term Fuel Trim near +25%. Refer to "Diagnostic Aids" on facing page of DTC 44 or

DTC 64 in Section 6C1-2A of the VX Series Service Information.

- Rich - Long Term Fuel Trim near - 22%. Refer to "Diagnostic Aids" on facing page of DTC 45 or

DTC 65 in Section 6C1-2A of the VX Series Service Information.

• CHECK: Fuel Control Module operation. Refer to TABLE A-4.1-1 of the VX Series Service Information.

• CHECK: Fuel pressure, refer to TABLE A-4.3 in Section 6C1-2A of the VX Series Service Information.

ADDITIONAL CHECKS

• CHECK: Vacuum leaks.

• CHECK: TCC operation, TCC applying too soon.

• CHECK: For correct PROM being installed into the PCM.

• CHECK: Service Bulletins for updates.

HESITATION, SAG, STUMBLE

Definition: Momentary lack of response as the accelerator is pushed down. Can occur at all vehicle speeds.

Usually most sever e when fir st tr ying to mak e the c ar move, as f r om a stop s ign. May cause engine to stall if sever e

enough.

PRELIMINARY CHECKS

Perform the careful visual/physical checks as described at the start of this Section -

"IMPORTANT PRELIMINARY CHECKS ".

Time or distance interval since normal engine tune-up has perform ed. Refer to time/distance intervals specified in

Owner's Manual.

• CHECK: Vacuum hoses for splits, kinks, and proper connections.

• CHECK: For vacuum leaks at throttle body mounting and inlet manifold.

SENSORS

• CHECK: TP Sensor - Check TP Sensor for binding or sticking. Voltage should increase at a steady rate as

throttle is moved toward W ide Open Throttle (W OT), refer TABLE A - 6.2 in Section 6C1-2A of the

VX Series Service Information.

• CHECK: MAF sensor, refer to TABLE A - 6.1 in Section 6C1-2A of the VX Series Service Information.

• CHECK: Engine coolant temperature sensor resistance. Refer to Diagnostic Trouble Code 14 in Section

6C1-2A of the VX Series Service Information for engine coolant temperature sensor temperature -

resistance table.

IGNITION SYSTEM

• CHECK: Spark plugs for being fouled, or for there being faulty secondary wiring.

• CHECK: Ignition system earth, CKT 453.

FUEL SYSTEM

• CHECK: Fuel pressure, refer use TABLE A - 4.3 in Section 6C1-2A of the VX Series Service Information.

• CHECK: Contaminated or incorrect fuel.

• CHECK: Canister purge system for proper operation.

• CHECK: Fuel injectors. Perform injector balance test.

ADDITIONAL CHECKS

• CHECK: Service Bulletins for updates.

• CHECK: Exhaust system back pressure, refer TABLE A-13 "RESTRICTED EXHAUST SYSTEM TEST" in

Section 6C1-2A of the VX Series Service Information.

• CHECK: Engine thermostat functioning correctly and proper heat range.

• CHECK: Generator output voltage. Repair if less than 9 or more than 16 volts.

CUTS OUT, MISSES

Definition: Steady pulsation or jerking that follows engine speed, usually more pronounced as engine load

increases. The exhaust has a steady spitting sound at idle or under load.

PRELIMINARY CHECKS

Perform the careful visual/physical checks as described at start of this Section -

"IMPORTANT PRELIMINARY CHECKS".

IGNITION SYSTEM

• CHECK: If ignition system is suspected of causing a miss at idle or cutting out under load.

• CHECK: If the previous checks did not find the problem;

Visually inspect ignition system fo r moistur e, dus t, cr ac ks, burns , etc . Spray plug wir es with fine water

mist to check for shorts.

Check for a misfiring cylinder at idle by:

1. Start engine, then dis connect IAC m otor . Rem ove one s park plug wire at a time us ing insulated pliers . Do

not run engine for long periods of time with any spark plug disconnected. The unburned fuel causes the

catalytic converter to be abnormally hot, and damage may occur if allowed to run this way too long.

2. If there is an rpm drop on all cylinders (equal to within 50 RPM), go to

ROUGH, UNSTABLE, OR INCORRECT IDLE, STA LLING symptom. Reconnect IAC motor.

3. If there is no rpm drop on one or more cylinders, or excessive variation in drop, check for spark on the

suspected cylinder(s) with ST-125 Spark Checking Tool or equivalent. If no spark, check plug lead for

excessive resistance (or possibly `open'). If there is spark, remove spark plug(s) in those cylinders and

check for:

- Cracks - Wear

- Improper Gap - Burned Electrodes

- Heavy Deposits

ENGINE MECHANICAL

• CHECK: Compression. Perform compression check on questionable cylinder(s) found above. If compression

is low, repair as necessary. Disconnect fuse F31 before checking.

• CHECK: Base engine. Remove rocker covers. Check for bent pushrods, worn rocker arms, broken valve

springs, worn camshaft lobes and valve timing, repair as necessary .

FUEL SYSTEM

• CHECK: Fuel system - Blocked fuel filter, low pressure, refer TABLE A-4.3 in Section 6C1-2A of the VX Series

Service Information.

• CHECK: Contaminated or incorrect fuel.

• CHECK: Perf ormance of injector . If there is good spark and com pression on all cylinders, check for res tricted

or non-operating fuel injectors. To check for a non-operating injector:

With the engine idling, check for clicking sound at each injector with a stethoscope or long

screwdriver held on the body of each injector. If any injector fails to make the clicking sound,

disconnect the electrical connector, and connect a suitable test light, such as BT-8329, across the

harness connec tor ter m inals. If the test light blink s with the engine idling, replace the inj ector . If there

is no blinking light, check for an "open" wire leading to that injector. Refer to Fuel Injector Circuit

Diagnosis TABLE 3.1 in Section 6C1-2C of the VX Series Service Information.

ADDITIONAL CHECKS

• CHECK: For EMI interference. A missing condition can be caused by Electromagnetic Interference (EMI) on

the reference circuit. EMI can usually be detected by monitoring engine RPM with a scan tool. A

sudden increas e in RPM with little c hange in actual engine RPM change, indicates EMI is pr esent. If

the problem exists, check routing of secondary wires, check earth circuit.

• CHECK: Inlet and exhaust manifold passage for casting flash.

ROUGH, UNSTABLE, OR INCORRECT IDLE , STALLING

Definition: Engine runs unevenly at idle. If bad enough, the vehicle may shake. Also, the idle may vary in RPM

(called "hunting"). Either condition may be bad enough to cause stalling. Engine idles at incorrect speed.

PRELIMINARY CHECKS

Perform the careful visual/physical checks as described at the start of this Section -

"IMPORTANT PRELIMINARY CHECKS".

• CHECK: For vacuum leaks, they will cause a fast idle.

• CHECK: PCM earths for being clean, tight and in there proper location. Refer to PCM wiring diagrams.

• CHECK: Idle Air Control ( IAC) system f or proper operation, refer T ABL E A-7.1 IG NIT ION SY STEM in Sec tion

6C1-2A of the VX Series Service Information.

• CHECK: For proper ignition voltage output using spark tester ST-125 or 7230.

• CHECK: Spark plugs. Remove spark plugs, checks for wet plugs cracks, wear, improper gap, burned

electrodes, or heavy deposits.

ENGINE MECHANICAL

• CHECK: Perform a cylinder compression check. Disconnect fuse F31 before checking.

• CHECK: For correct camshaft valve lift and timing or weak valve springs.

FUEL SYSTEM

• CHECK: For contaminated or incorrect fuel.

• CHECK: For injectors that are restricted or not operating.

• CHECK: For injectors leaking, or incorrect fuel pressure, refer TABLE A-4.3 in Section 6C1-2A of the VX

Series Service Information.

• NOTE: Monitoring Long term fuel trim will help identify the cause of the problem. If the system is running lean

(Long Term Fuel Trim near +25%), refer to "Diagnostic Aids" on facing page of DTC 44 or

DTC 64 in Section 6C1-2A of the VX Series Service Inform ation. If the system is running rich (Long

Term Fuel Trim near -22%), refer to "Diagnostic Aids" on facing page of DTC 45 or DTC 65 in

Section 6C1-2A of the VX Series Service Information.

• CHECK: Injector balance.

• CHECK: For fuel in pressure regulator hose. If fuel is present, replace regulator assembly.

• CHECK: The Oxygen Sensor (O2S) should respond quickly to different throttle positions, if it does not, check

the Oxygen Sensor (O2S) for silicon contamination from fuel, or use of improper RTV sealant. The

sensor will have a white, powdery coating, and will result in a high but false signal voltage (rich

exhaust indication). The PCM will then reduce the amount of fuel delivered to the engine, causing a

severe driveability problem.

ADDITIONAL CHECKS

• CHECK: MAF sensor, refer to TABLE A-6.1 in Section 6C1-2A of the VX Series Service Information.

• CHECK: Throttle linkage for sticking or binding.

• CHECK: IAC operation, refer TABLE A-7.1 in Section 6C1-2A of the VX Series Service Information.

• CHECK: A/C signal to PCM, scan tool should indicate A/C is being requested whenever A/C is selected and

the blower switch is "ON." If problem exists with A/C "ON," check A/C system operation

TABLE A-11.1 or TABLE A-11.3 in Section 6C1-2A of the VX Series Service Information.

• CHECK: PCV valve for proper operation by placing finger over inlet hole in valve end several times. Valve

should snap back. If not, replace valve.

• CHECK: Service Bulletins for updates.

• CHECK: For broken motor mounts.

• CHECK: Generator output voltage. Repair if less than 9 or more than 16 volts.

• CHECK: Battery cables and ear th straps should be clean and s ecure. Err atic voltage will cause IAC to c hange

its position resulting in poor idle quality.

POOR FUEL ECONOMY

Definition: Fuel ec onomy, as measur ed by an actual road tes t, is notic eably lower than expected. Also, economy is

noticeably lower than it was on this vehicle at one time, as previously shown by an actual road test.

A misfiring engine will have excessive unburned oxygen in the exhaust, and the "Closed-Loop" fuel control

system oxygen sensor will interpret a lean exhaust. The PCM will cause an increase in fuel injector

pulsewidth in attempts to overcome the lean exhaust indication.

PRELIMINARY CHECKS

Perform the careful visual checks as described at the start of this Section -

"IMPORTANT PRELIMINARY CHECKS".

Visually/physically check: Vacuum hoses for splits, kinks, and proper connections

Check owner's driving habits.

- Is A/C "ON" full time (Defroster mode "ON")?

- Are tires at correct pressure?

- Are excessively heavy loads being carried?

- Is acceleration too much, too often?

Check air cleaner element (filter) for dirty or being plugged.

Check for correct size tyres. Oversize tyres will cause speedometer/odometer to be "slow," and indicated fuel usage

may increase.

IGNITION SYSTEM

• CHECK: Spark plugs. Remove spark plugs, check for wet plugs, cracks, wear, improper gap, burned

electrodes, or heavy deposits. Repair or replace as necessary.

COOLING SYSTEM

• CHECK: Engine coolant level.

• CHECK: Engine thermostat for faulty part (always open) or for wrong heat range.

ENGINE MECHANICAL

• CHECK: Compression. Disconnect fuse F31 before checking.

ADDITIONAL CHECKS

• CHECK: TCC operation. A scan tool should indicate an rpm drop, when the TCC is commanded "ON."

• CHECK: For dragging brakes.

• CHECK: For exhaust system restriction, refer to TABLE A-13 in Section 6C1-2A of the VX Series Service

Information.

• CHECK: For proper calibration of speedometer.

• CHECK: Induction system and crankcase for air leaks.

BACKFIRE

Definition: Fuel ignites in inlet manifold, or in exhaust system, making loud popping noise.

PRELIMINARY CHECKS

Perform the careful visual/physical checks as described at the start of this Section -

" IMPORTANT PRELIMINARY CHECKS ".

IGNITION SYSTEM

• CHECK: Proper ignition coil output voltage with spark tester ST-125 or 7230.

• CHECK: Spark plugs. Remove spark plugs, check for wet plugs, cracks, wear, improper gap, burned

electrodes, or heavy deposits. Repair or replace as necessary.

• CHECK: Spark plug wires for c rossf ire, also inspec t distributor ass embly, spark plug wires, and pr oper routing

of plug wires.

ENGINE MECHANICAL

• CHECK: Compression - Look for sticking or leaking valves. Remove fuse F31 before performing check.

• CHECK: Valve timing.

• CHECK: Inlet and exhaust manifold passages for casting flash.

FUEL SYSTEM

• CHECK: Perform "Fuel System Diagnosis Check", refer TABLE A-4.3. in Section 6C1-2A of the VX Series

Service Information.

EXCESSIVE EXHAUST EMISSIONS OR ODOURS

Definition: Vehicle fails an emission test. Vehicle has excessive "rotten egg" smell. Excessive odours do not

necessarily indicate excessive emissions.

PRELIMINARY CHECKS

Perform "On-Board Diagnostic Sy stem Check" in Section 6C1-2A of the VX Series Service Information.

IGNITION SYSTEM

• CHECK: Spark plugs. Remove spark plugs, check for wet plugs, cracks, wear, improper gap, burned

electrodes, or heavy deposits. Repair or replace as necessary.

COOLING SYSTEM

If the scan tool indicates a very high engine coolant temperature and the system is running lean:

• CHECK: Engine coolant level.

• CHECK: Engine thermostat for faulty part (always open) or for wrong heat range.

• CHECK: Cooling fan operation.

FUEL SYSTEM

• CHECK: For contaminated or incorrect fuel.

• NOTE:· If the system is running RICH (Long Term Fuel Trim near -22%) - Refer to "Diagnostic Aids" on

facing page of DTC 45 or DTC 65 in Section 6C1-2A of the VX Series Service Information. If the

system is running LEAN (Long Term Fuel Trim near +25%) - Refer to "Diagnostic Aids" on facing

page of DTC 44 or DTC 64 in Section 6C1-2A of the VX Series Service Information.

• CHECK: For properly installed fuel cap.

• CHECK: Fuel pressure, refer TABL E A-4.3 in Section 6C1-2A of the VX Series Service Information.

• CHECK: Canister for fuel loading.

ADDITIONAL CHECKS

• CHECK: For vacuum leaks.

• CHECK: Burnt valves.

• CHECK: For lead contamination for catalytic converter (look for the removal of fuel filler neck restriction).

• CHECK: Carbon build-up. Remove carbon with top engine cleaner. Follow instructions on can.

• CHECK: For exhaust system restriction, refer TABLE A-13 in Section 6C1-2A of the VX Series Service

Information.

• CHECK: PCV valve for being plugged or stuck, or fuel in the crankcase.

• CHECK: Service Bulletins for updates.

DIESELING, RUN-ON

Definition: Engine continues to run after ignition is turned "OFF," but runs very roughly.

PRELIMINARY CHECKS

- Perform the careful visual/physical checks as described at the start of the VX Series Service Information -

"IMPORTANT PRELIMINARY CHECKS".

FUEL SYSTEM

• CHECK: Injectors for leaking. Perform "Fuel System Diagnosis Check", refer TABLE A-4.3 in Section 6C1-

2A of the VX Series Service Information.

IGNITION SYSTEM

• CHECK: If engine runs smoothly, check ignition switch and adjustment.

RICH/LEAN SYMPTOM TABLE

Circuit Description:

The Rich/Lean Symptom Table is an organised appr oach to identifying a driveability com plaint that may be caused

by an overric h or overlean oper ating condition. Unders tanding the Table and us ing it corr ectly will reduce diagnostic

time and improve customer satisfaction. Start at the left side of the Table and work to the right.

Test Description:

Numbers below refer to step number(s) on the diagnostic Table.

1. This is a partial list of possible customer complaints and what the air/fuel mixture must be to cause such a

condition.

2. A lean exhaust m eans that ther e is a lot of oxygen in the exhaust stream . Lots of oxygen in the exhaust str eam

means a low oxygen sensor signal voltage. Lean=lots of oxygen=low oxygen sensor signal voltage. A rich

exhaust means that there is a lot of fuel and very little oxygen in the exhaust stream.

3. The oxygen sensor signal to the PCM determines what the PCM should do to compensate for the present

condition. Depending upon the severity of the problem , the PCM will compensate f or the condition by changing

the short term fuel trim and short term fuel trim values either higher or lower. An short term fuel trim value

above 0% m eans the PCM will add m or e f uel to the engine, by increasing the injector pulsewidth, thus making a

lean engine run richer. A s hort term f uel trim value below 0% m eans the PCM will decr ease the am ount of fuel

to the engine, by decreasing the injector pulse width, thus making a rich engine run leaner.

4. This list represents areas where you should look to find the root cause of the customer complaint. Not every

cause of the symptom is listed here, however, the items listed provide a good general description of areas to

look at.

Diagnostic Aids:

Driveability complaints may be caused by the PCM, system components or electrical faults, however, a basic engine

problem may also present a symptom sim ilar to an electr ical failure. Rem em ber to check the air cleaner and all the

basic engine components, there could be worn rings, worn camshaft lobes, collapsed lifters, misaligned timing

chain, vacuum leaks etc.

RICH/LEAN SYMPTOM TABLE

VEHICLE OPERATION OXYGEN SENSOR

OPERATION SHORT AND LONG TERM

FUEL TRIM OPERATION POSS IBLE CAUSES

CUSTOMER

DRIVEABILITY

COMPLAINT/SYMPTOM

EXHAUST

STREAM

STATUS

OXYGEN

SENSOR

VOLTAGE

LEAN Air/Fuel Mixture

Short Term Fuel Trim and Long Term Fuel

Trim are numerically increasing High

LEAN

Air/Fuel M i xture

+100

(above 0%) possible DTC 44 or DTC 64.

Oxygen Sensor voltage between 450 mV

and 0 mV.

- High NoX Emissions High

Oxygen 0 mV Cause: Fuel system not in control.

Check For:

- Stumbles/Stalls Content • Poor PCM earths

- Surges • Vacuum leak, intake manifold leak

- Poor Performance LEAN

EXHAUST

+25% • Restricted fuel filter

• Low fuel pressure

RICH

COMMAND • Water contamination in fuel

• Lean (restricted flow), fuel injector(s)

ADD

FUEL Oxygen Sensor being “Tricked” Lean.

Cause: Too much air in exhaust stream

above OXYGEN SENSOR.

16 to 1

Air/Fuel M i xture • Cylinders not firing (misfire) sending

unburned air/fuel mixture into exhaust

Increase

Injector pulse width • Cracked or leaking exhaust manifold

• Oxygen sensor mounting is loose, dirty

or has no sealing washer

14.7 to 1

Air/Fuel M i xture

450 mV

0% No

Change

RICH Air/Fuel Mixture

Short Term Fuel Trim and Long Term Fuel

Trim are munerically decreasing low

Decrease

Injector Pluse Width (below 0%) possible DTC 45 or DTC 65.

13 to 1

Air/Fuel M i xture

Oxygen Sensor voltage between 450 mV

and 1000 mV.

REMOVE

FUEL Cause: Fuel system not in control

Check For:

• Restricted (dirty) air filter

RICH

Air/Fuel M i xture

LEAN

COMMAND • Leaking injector(s)

• High fuel pressure

• Restricted fuel return line

- High HC, CO

Emissions • ECT temperature value low

- Black Smoke • Oxygen Sensor contaminated

(covered w/ foreign substance)

- Catalytic Converter Odor -22%

• Engine oil contaminated with fuel

- Fouled Spark Plugs RICH

EXHAUST 1000 mV

• Canister purge continuously purging

Oxygen Sensor being “Tricked” Rich.

Cause: Not enough air in exhaust.

Low • Restricted exhaust system

Oxygen

Content -100% • Oxygen Sensor earth, wire open, or has

a poor connection

• Oxygen Sensor poisoned

(impregnated w/ foreign substance)

• When using a Scan tool to observe short term fuel trim and long term fuel trim values, remember that if the system is in control, no action is required unless

there is a driveability symptom present.

AUTOMATIC TRANSMISSION SYMPTOM TABLES

Oil Pressure High or Low

Checks Causes

Oil Pump Assembly • Pressure regulator valve stuck

• Pressure regulator valve spring

• Rotor guide omitted or disassembled

• Rotor cracked or broken

• Reverse boost valve or sleeve stuck, damaged or incorrectly assembled

• Orifice hole in pressure regulator valve plugged

• Sticking slide or excessive rotor clearance

• Pressure relief ball not seated or damaged

• Porosity in pump cover or body

• Wrong pump cover

• Pump faces not flat

• Excessive rotor clearance

Oil Filter • Intake pipe restricted by casting flash

• Cracks in filter body or intake pipe

• O-ring seal missing, cut or damaged

• Wrong grease used on rebuild

Valve Body • Manual valve scored or damaged

• Spacer plate or gaskets incorrect, misassembled or damaged

• Face not flat

• 2-3 Shift valve stuck

• Checkballs omitted or misassembled

Pressure Control

Solenoid Valve Damage to pins

TFP Val Position Sw. • Contamination

• Damaged seals

Case Case to valve body face not flat

Harsh Shifts

Checks Causes

Throttle Position Sensor Open or shorted circuit

Vehicle Speed Sensor Open or shorted circuit

TFP Val Position Sw. • Contamination

• Damaged seals

Trans Fluid Temperature

Sensor Open or shorted circuit

Engine Coolant

Temperature Sensor Open or shorted circuit

Pressure Control

Solenoid Valve • Damage to pins

• Contamination

Inaccurate Shift Points

Checks Causes

Oil Pump Assembly • Stuck pressure regulator valve

• Sticking pump slide

Valve Body Assembly Spacer plate or gaskets misassembled, damaged or incorrect

Case • Porous or damaged valve body pad

• 2-4 Servo Assembly:

-2-4 accumulator porosity

-Damaged servo piston seals

-Apply pin damaged or improper length

• 2-4 Band Assembly:

-Burned

-Anchor pin not engaged

TP Sensor • Disconnected

• Damaged

Vehicle Speed Sensor • Disconnected

• Damaged

• Bolt not tightened

1st Gear Range Only-No Upshift

Checks Causes

Valve Body • The 1-2 Shift valve is sticking

• The spacer plate or gaskets are mispositioned or damaged

Case The case to valve body face is damaged or is not flat

Shift Solenoid Valves • Stuck or damaged

• Faulty electrical connection

2-4 Servo Assembly • The apply passage case is restricted or blocked

• Nicks or burrs on the servo pin or on the pin bore in the case

• Fourth servo pistons installed backwards

2 - 4 Band Assembly • The 2-4 band is worn or damaged

• The band anchor pin is not engaged

Slips in 1st Gear

Checks Causes

Forward Clutch

Assembly • Clutch plates worn

• Porosity or damage in forward clutch piston

• Forward clutch piston inner and outer seals missing, cut or damaged

• Damaged forward clutch housing

• Forward clutch housing retainer and ball assembly not sealing or damaged

Forward Clutch

Accumulator • Piston seal missing, cut or damaged

• Piston out of its bore

• Porosity in the piston or valve body

• Stuck abuse valve

Input Housing and Shaft

Assembly Turbine shaft seals missing, cut or damaged

Valve Body • 1-2 Accumulator valve stuck

• Face not flat, damaged lands or interconnected passages

• Spacer plate or gaskets incorrect, mispositioned or damaged

Low Roller Clutch • Damage to lugs to inner ramps

• Rollers not free moving

• Inadequate spring tension

• Damage to inner splines

• Lube passage plugged

Torque Converter Stator roller clutch not holding

1-2 Accumulator

Assembly • Porosity in piston or 1-2 Accumulator cover and pin assembly

• Damaged ring grooves on piston

• Piston seal missing, cut or damaged

• Valve body to spacer plate gasket at 1-2 Accumulator cover, missing or damaged

• Leak between piston and pin

• Broken 1-2 Accumulator spring

Line Pressure Refer to Oil Pressure High or Low

2-4 Servo Assembly 4th Servo piston in backward

Slipping or Rough 1-2 Shift

Checks Causes

Valve Body Assembly • 1-2 Shift valve train stuck

• Gaskets or spacer plate incorrect, mispositioned or damaged

• 1-2 Accumulator valve stuck

• Face not flat

2-4 Servo Assembly • Apply pin too long or too short

• 2nd servo apply piston seal missing, cut or damaged

• Restricted or missing oil passages

• Servo bore in case damaged

2nd Accumulator • Porosity in 1-2 accumulator housing or piston

• Piston seal or groove damaged

• Nicks or burrs in 1-2 accumulator housing

• Missing or restricted oil passage

2-4 Band Worn or mispositioned

Oil Pump Assembly or

Case Faces not flat

No 2-3 Shift or 2-3 Shift Slips, Rough or Hunting

Checks Causes

Valve Body Assembly • 1-2 Shift valve train stuck

• Gaskets or spacer plate incorrect, mispositioned or damaged

• 1-2 Accumulator valve stuck

• Face not flat

2-4 Servo Assembly • Apply pin too long or too short

• 2nd servo apply piston seat missing, cut or damaged

• Restricted or missing oil passages

• Servo bore in case damaged

2nd Accumulator • Porosity in 1-2 accumulator housing or piston

• Piston seal or groove damaged

• Nicks or burrs in 1-2 accumulator housing

• Missing or restricted oil passage

2-4 Band Worn or mispositioned

Oil Pump Assembly or

Case Faces not flat

2nd/3rd Gears Only or 1st/4th Gears Only

Checks Causes

Shift Solenoid Valves • Sediment is in the valves

• The electrical connection is faulty

• Damaged seal

Third Gear Only

Checks Causes

DTC 81 • The electrical connection is faulty

• Shorted or damaged

3-2 Flare or Tie-Up

Checks Causes

3-2 Shift Solenoid • Shorted or damaged

• Contamination

• Damaged Seal

No 3-4 Shift, Slips or Rough 3-4 Shift

Checks Causes

Oil Pump Assembly • Pump cover retainer and ball assembly omitted or damaged

• Faces not flat

Valve Body Assembly • Valves stuck:

-2-3 Shift valve train

-Accumulator valve

-1-2 Shift valve train

-3-2 Shift valve

• Spacer plate or gasket incorrect, mispositioned or damaged

2-4 Servo Assembly • Incorrect band apply pin

• Missing or damaged servo seals

• Porosity in piston, cover or case

• Damaged piston seal grooves

• Plugged or missing orifice cup plug

Case • 3rd Accumulator retainer and ball assembly leaking

• Porosity in 3-4 accumulator piston or bore

• 3-4 Accumulator piston seal or seal grooves damaged

• Plugged or missing orifice cup plug

• Restricted oil passage

Input Housing Assembly Refer to Slipping 2-3 Shift

2-4 Band Assembly Worn or Disassembled

No Reverse or Slips in Reverse

Checks Causes

Input Housing Assembly • 3-4 Apply ring stuck in applied position

• Forward clutch not releasing

• Turbine shaft seals missing, cut or damaged

Manual Valve Link Disconnected

Valve Body Assembly • 2-3 Shift valve stuck

• Manual linkage not adjusted

• Spacer plate and gaskets incorrect, mispositioned or damaged

• Lo overrun valve stuck

• Orificed cup plug restricted, missing or damaged

Reverse Input Clutch

Assembly • Clutch plate worn

• Reverse input housing and drum assembly cracked at weld

• Clutch plate retaining ring out of groove

• Return spring assembly retaining ring out of groove

• Seals cut or damaged

• Restricted apply passage

• Porosity in piston

• Belleville plate installed incorrectly

• Excessive clutch plate travel

• Oversized housing

Lo and Reverse Clutch • Clutch plates worn

• Porosity in piston

• Seals damaged

• Return spring assembly retaining ring mispositioned

• Restricted apply passage

No Part Throttle or Delayed Downshifts

Checks Causes

Input Housing Assembly • 3-4 Apply ring stuck in applied position

• Forward clutch not releasing

• Turbine shaft seals missing, cut or damaged

Manual Valve Link • Disconnected

Valve Body Assembly • 2-3 Shift valve stuck

• Manual linkage not adjusted

• Spacer plate and gaskets incorrect, mispositioned or damaged

• Lo overrun valve stuck

• Orificed cup plug restricted, missing or damaged

Reverse Input Clutch

Assembly • Clutch plate worn

• Reverse input housing and drum assembly cracked at weld

• Clutch plate retaining ring out of groove

• Return spring assembly retaining ring out of groove

• Seals cut or damaged

• Restricted apply passage

• Porosity in piston

• Belleville plate installed incorrectly

• Excessive clutch plate travel

• Oversized housing

Lo and Reverse Clutch • Clutch plates worn

• Porosity in piston

• Seals damaged

• Return spring assembly retaining ring mispositioned

• Restricted apply passage

Harsh Garage Shift

Checks Causes

Valve Body Assembly • Orifice cup plug missing

• Checkball missing

No Overrun Braking - Manual 3-2-1

Checks Causes

External Linkage Not adjusted properly

Valve Body Assembly • 4-3 Sequence valve stuck

• Checkball mispositioned

• Spacer plate and gaskets incorrect, damaged or mispositioned

Input Clutch Assembly • Turbine shaft oil passages plugged or not drilled

• Turbine shaft seal rings damaged

• Turbine shaft sealing balls loose or missing

• Porosity in forward or overrun clutch piston

• Overrun piston seals cut or damaged

• Overrun piston checkball not sealing

No TCC Apply

Checks Causes

Electrical • 12 Volts not supplied to transmission

• Outside electrical connector damaged

• Inside electrical connector, wiring harness or solenoid damaged

• Electrical short (pinched solenoid wire)

• Solenoid not earthed

Converter Internal damage

Oil Pump Assembly • Converter clutch valve stuck or assembled backwards

• Converter clutch valve retaining ring mispositioned

• Pump to case gasket mispositioned

• Orifice cup plug restricted or damaged

• Solenoid O-ring seal cut or damaged

• High or uneven bolt torque (pump body to cover)

Input Housing and Shaft • Turbine shaft O-ring seal cut or damaged

• Turbine shaft retainer and ball assembly restricted or damaged

TFP Val Position Switch • Contamination

• Damaged seals

Valve Body Assembly • TCC signal valve stuck

• Solenoid O-ring leaking

Solenoid Screen Blocked

TCC Solenoid Valve —

Engine Speed Sensor —

Engine Coolant

Temperature Sensor —

DTCs 19, 21, 22, 28, 67,

81, 83, 84 —

Automatic Transmission

Fluid Temperature

Sensor

—

Torque Converter Clutch Shudder

Checks Causes

Electrical • 12 Volts not supplied to transmission

• Outside electrical connector damaged

• Inside electrical connector, wiring harness or solenoid damaged

• Electrical short (pinched solenoid wire)

• Solenoid not earthed

Converter Internal damage

Oil Pump Assembly • Converter clutch valve stuck or assembled backwards

• Converter clutch valve retaining ring mispositioned

• Pump to case gasket mispositioned

• Orifice cup plug restricted or damaged

• Solenoid O-ring seal cut or damaged

• High or uneven bolt torque (pump body to cover)

Input Housing and Shaft • Turbine shaft O-ring seal cut or damaged

• Turbine shaft retainer and ball assembly restricted or damaged

TFP Val Position Switch • Contamination

• Damaged seals

Valve Body Assembly • TCC signal valve stuck

• Solenoid O-ring leaking

Solenoid Screen Blocked

No TCC Release

Checks Causes

TCC Solenoid Valve • Internal earth

• Clogged exhaust orifice

Converter Internal damage

Valve Body Assembly The converter clutch apply valve is stuck in the apply position

Oil Pump Assembly The converter clutch valve is stuck

PCM External earth

Drives in Neutral

Checks Causes

Forward Clutch The clutch does not release

Manual Valve Link Disconnected

Case • The face is not flat

• Internal leakage exists

2nd Gear Start

Checks Causes

Forward Clutch Sprag

Assembly The sprag assembly is installed backward

No Park

Checks Causes

Parking Linkage • Actuator rod assembly bent or damaged

• Actuator rod spring binding or improperly crimped

• Actuator rod not attached to inside detent lever

• Parking lock bracket damaged or not torqued properly

• Inside detent lever not torqued properly

• Parking pawl binding or damaged

Oil Out the Vent

Checks Causes

Oil Pump Chamber in pump body rotor pocket

Miscellaneous Fluid level - overfilled

Vibration in Reverse and Whining Noise in Park

Checks Causes

Oil Pump Chamber in pump body rotor pocket

Miscellaneous Fluid level - overfilled

Ratcheting Noise

Checks

Causes

Parking Pawl The parking pawl return spring is weak, damaged, or misassembled

No Drive in All Ranges

Checks

Causes

Torque Converter The converter to flex plate bolts are missing

No Drive in Drive Range

Checks Causes

Torque Converter • The stator roller clutch is not holding

• The converter is not bolted to the flex plate

Front Oil Leak

Checks Causes

Torque Converter • The welded seam is leaking

• The converter hub is damaged

Torque Converter Seal • The seal assembly is damaged

• The garter spring is missing

Delay in Drive and Reverse

Checks Causes

Torque Converter Converter drainback

PCM CONNECTOR SYMPTOM TABLES

The following Powertrain Control Module (PCM) connector Symptoms Tables identifies the function of each pin of

the PCM connector, the c irc uit number, the wire colour , and the cavity of the component to which the wire connec ts.

The left colum n in this T able lists the PCM connec tor pins in as cending order. T he T able m ay also be entered from

the right-most column, which lists possible symptoms that may be caused by a fault in each of the circuits. If a

problem in any of these circuits will cause a Diagnostic Trouble Code to be set, the DTC's are identified in the

second column from the right edge of the Table. (However, if a DTC has been s et, you should attem pt to diagnose

the condition using Section 6C1-2A DIAGNOSTIC TABLES - V6 ENGINE of the VX Series Service Information

before diagnosing by symptom.) The expected normal voltage for each circuit is shown for two conditions. Check

the voltage with the ignition "ON" but the engine not running, and with the engine running. Both check s are r equired

for accurate diagnosis. Reference notes are made for some circuits. These notes state conditions that cause

varying voltages or mention unique characteristics of the circuit. To measure the voltages, backprobe the PCM

connector. Whenever backprobing, be careful not to damage the connector. Careless backprobing may damage the

connector seal and/or terminal. Damaged pins will provide incorrect readings and cause additional system

problems.

PCM CONNECTOR A

POWERTRAIN CONTROL MODULE CONNECTOR “A” SYMPTOMS TABLE

PINK 24 PIN A - B CONNECTOR

CKT

WIRE

COMPONENT/ NORMAL

VOLTAGES

DTCS

POSSIBLE SYMPTOMS

FROM

PIN FUNCT ION # COLOUR CONNECTOR CAVITY IGN

“ON” ENG

RUN AFFECTED FAULTY CIRCUIT

A1 SYSTE M EA RTH 750 B/R OXYGE N S ENSOR AND

ENGINE EARTH “E” * * NONE NO ST ART IF ALL

EARTH CIRCUITS ARE

OPEN.

A2 SYSTEM EARTH 750 B/R ENGINE EARTH “F” * * NONE NO START IF A LL

EARTH CIRCUITS ARE

OPEN.

A3 PRIMARY

SERIAL

DATA

1221 R/B “DLC” 9 & BCM 3-5 3-5 31 NO SERIA L DATA.

NO CRANKING.

A4 FUSED IGNITION

FEED 39 P/B FUSE F14 12 13 NONE NO “CHECK

POWERTRAIN”

LAMP.

NO START.

A5 NOT USED - - - - - - -

A6 FUEL PUMP

RELAY

CONTROL

465 G/W FUEL P UMP RE LAY “2” (4)

(2) 13 NONE HARD TO START , LONG

CRANK TIME, SEE

TABLE A-1.

A7 TP SENSOR

REFERENCE

VOLTAGE

416 GY TP SENSOR “A” 5 5 21, 22 ROUGH IDLE .

A8 BATTERY

VOLTAGE FEED 740 O/B FUSE F31 12 13 NONE NO START.

A9 NOT USED - - - - - - -

A10 NOT USED - - - - - - -

A11 NOT USED - - - - - - -

A12 NOT USED - - - - - - -

(2)

(4)

12 VOLTS FOR FIRST TWO SECONDS AFTER IGNITION IS TURNED “ON” WITHOUT CRANKING THE ENGINE.

12 VOLTS WHEN FUEL P UMP IS RUNNING.

LESS THA N 0. 50 V OLT.

REFER T O WIRING DI AGRAMS.

PCM CONNECTOR B

POWERTRAIN CONTROL MODULE CONNECTOR “B” SYMPTOMS TABLE

PINK 24 PIN A - B CONNECTOR

CKT

WIRE

COMPONENT/ NORMAL

VOLTAGES

DTCS

POSSIBLE SYMPTOMS

FROM

PIN FUNCT ION # COLOUR CONNECTOR CAVITY IGN

“ON” ENG

RUN AFFECTED FAULTY CIRCUIT

B1 SYSTEM EA RTH 750 B/R * * NONE NO ST A RT I F A LL

EARTH CIRCUITS ARE

OPEN.

B2 SYSTEM EA RTH 750 B/R * * NONE NO ST A RT I F A LL

EARTH CIRCUITS ARE

OPEN.

B3 A/C PRESSURE

SENSOR SIGNAL 259 G/B A/C PRESSURE

SENSO R “C” 1-2 1-2 95 INOP A/C SYSTEM.

B4 INTAKE AIR

TEMPERATURE

SENSOR

472 BR IAT SE NS OR “B” 1.0

(6) 1.0

(6) 23, 25, 26 NONE.

B5 ECT SENSOR

SIGNAL 410 Y ECT SENSOR 1.9

(6) 1.9

(6) 14, 15, 16 HARD START.

LONG CRANK TIME.

B6 TFT SENSOR

SIGNAL 1227 B/Y TRANSMISSION PASS-

THRU

CONNECTOR “L” TFT

SENSOR “A”

1.8

(6) 1.8

(6) 58

59 MAXIMUM LINE

PRESSURE, TORQUE

CONVERTE R CLUT CH IN

SECOND, T HIRD AND

FOURTH GEAR.

B7 A/C

REFRIGERANT

PRESSURE

SENSOR

REFERENCE

VOLTAGE

415 V/W A/C PRESSURE

SENSOR TERMINAL B” 5 5 96 A/C INOP.

B8 BATTERY

VOLTAGE FEED 740 O/B FUSE F31 12 13 NONE NO START.

B9 NOT USED - - - - - - -

B10 NOT USED - - - - - - -

B11 TP SENSOR

SIGNAL 417 BLU THROTTLE POSITION

SENSO R “C” (5) (5) 21, 22 POOR PERF ORMANCE,

HIGH IDLE.

B12 INJECTOR

VOLTAGE

MONITOR LINE

481 R IGNITION AND FUEL

INJECTORS 12 13 57 NONE

(5)

(6)

0.25 - 1.25 VOLTS MEASURED B E T WEEN TERMINA LS “B11” AND “B1” OR AB OUT 4.0 VOLTS AT WIDE OPE N

THROTTLE.

VARIES WITH TEMPERATURE.

LESS THA N 0. 50 V OLT.

REFER T O WIRING DI AGRAMS.

PCM CONNECTOR C

POWERTRAIN CONTROL MODULE CONNECTOR “C” SYMPTOMS TABLE

PINK 32 PIN C - D CONNECTOR

CKT

WIRE

COMPONENT/ NORMAL

VOLTAGES

DTCS

POSSIBLE SYMPTOMS

FROM

PIN FUNCT ION # COLOUR CONNECTOR CAVITY IGN

“ON” ENG

RUN AFFECTED FAULTY CIRCUIT

C1 TCC SOLENOID

“ON-OFF”

CONTROL

422 GY/R TORQUE CONVERTER

CLUTCH SOLENOID “B” 12 13 67

(9) NO TCC AND NO

FOURTH GEAR IF IN

HOT MODE.

C2 1-2 SHIFT

SOLENOID

CONTROL

1222 LG 1-2 SHIFT SOLENOID

TERMINAL “B” 12 * 82

(9) 2nd and 3rd GEAR ONLY

OR 1st AND 4th GEAR

ONLY AND MAXIMUM

LINE PRESSURE .

C3 2-3 SHIFT

SOLENOID

CONTROL

1223 Y/B 2-3 SHIFT SOLENOID

TERMINAL “B” 12 * 81

(9) POSSIBLY THIRD GEAR

ONLY, NO TCC

OPERATIO N , MAXIMUM

LINE PRESSURE .

C4 CANISTER

PURGE

SOLENOID

428 G/Y CANISTER PURGE

SOLENOI D TERMINAL

“B”

12 13 97 RICH EXHAUST.

C5 VEHICLE SPEED

SENSOR SIGNAL

SPEEDOMETER

123 V/W INSTRUMENT

CONNECTOR #17 (1) (1) NONE INOPERATIVE

SPEEDOMETER.

C6 VEHICLE SPEED

SENSOR SIGNAL

HIGH

831 BLU/W VEHICLE SPEED

SENSOR (1) (1) 24, 72,

94 MAXIMUM L INE

PRESSURE.

C7 IAC COIL “A”

HIGH 441 LBLU IDLE AIR CONTROL

VALVE “C” NOT USE

ABLE 35 STALLING, ROUGH,

UNSTAB LE OR

INCORRECT I DLE.

C8 IAC COIL “A”

LOW 422 LB LU/B IDLE AIR CONTROL

VALVE “D” NOT USE

ABLE 35 STALLING, ROUGH,

UNSTAB LE OR

INCORRECT I DLE.

C9 IAC COIL “B”

LOW 444 LG/B I DLE A IR CONTROL

VALVE “B” NOT USE

ABLE 35 STALLING, ROUGH,

UNSTAB LE OR

INCORRECT I DLE.

C10 IAC COIL “B”

HIGH 443 LG/B I DLE A IR CONTROL

VALVE “A” NOT USE

ABLE 35 STALLING, ROUGH,

UNSTAB LE OR

INCORRECT I DLE.

C11 TORQUE

REQUEST 1426 O/W ABS/TCS MODULE “13” 4-5 4-5 - -

C12 KNOCK SENSOR

(ESC) SIGNAL

INPUT

815 W/R KNOCK SENSOR 1.3

m/VAC 25.5

m/VAC 43

(9) LACK OF

PERFORMANCE, P OOR

FUEL ECONOMY.

C13 3-2 CONTROL

SOLENOID 897 G/W 3-2 CONTROL

SOLENOID “B” 12 * 66 SOFT LANDING INTO

THIRD GEAR STAY IN

THIRD GEA R

C14 3-2 CONTROL

FEEDBACK 897 G/W CONTROL CIRCUIT 12 * 66 SOFT LANDING INTO

THIRD GEAR STAY IN

THIRD GEA R

C15 TCC SOLENOID

PWM FEEDBACK 418 BR TCC CONTROL CI RCUIT 12 13 83 TCC INOP.

C16 TCC SOLENOID

PWM 418 BR TCC SOLENOI D “B” 12 13 83 TCC INOP.

(1)

(9)

VARIES FROM 0.10 TO ABOUT 13 V, DEPENDING ON POSITION OF DRIVE WHEELS WHEN VEHICLE IS MOVING.

OPEN/EARTHED CIRCUIT.

LESS THA N 0. 50 V OLT.

REFER T O WIRING DI AGRAMS.

PCM CONNECTOR D

POWERTRAIN CONTROL MODULE CONNECTOR “D” SYMPTOMS TABLE

PINK 32 PIN C - D CONNECTOR

CKT

WIRE

COMPONENT/ NORMAL

VOLTAGES

DTCS

POSSIBLE SYMPTOMS

FROM

PIN FUNCT ION # COLOUR CONNECTOR CAVITY IGN

“ON” ENG

RUN AFFECTE

D FAULTY CIRCUIT

D1 MAF SENSOR 792 BR/W MASS A IR FLOW

SENSOR TERMINAL “A” 4.8 4.2 32 RICH EXHAUST.

D2 NOT USED - - - - - - -

D3 CAMSHAFT

POSITION

SENSOR SIGNAL

630 B IGNITION MODULE “F” 4.8 4.4 48, 49 V-6 ONLY , NO

SEQUENTIAL FUEL

INJECTION.

D4 CRANKSHAFT

18X SIGNAL 647 LBLU/B IGNITION MODULE “C” 5 2.7

3.0

(9) NO START.

D5 VEHICLE SPEED

SENSOR SIGNAL

LOW

832 T VEHICLE SPEED

SENSOR * * 24, 72

94 MAXIMUM LI N E

PRESSURE SECOND

GEAR ONLY.

D6 NOT USED - - - - - - -

D7 NOT USED - - - - - - -

D8 NOT USED - - - - - - -

D9 BYPASS

CONTROL 424 T/B IGNI TION MODULE “B” 0 4.7 42 POOR PERFORMANCE.

D10 ELECTRONIC

SPARK TIMING

OUTPUT

423 W IGNITI ON MODULE “A” 0 2.0 41, 42 HARD TO ST A RT,

STALLS.

D11 REFERENCE

SIGNAL LOW 453 B/R IGNITION MODULE “L” * * NONE POOR PERFORMANCE.

D12 REFERENCE

SIGNAL HIGH 430 V I G NI TION MODULE “D” 4.8 2.3 12 NO START.

D13 RH O2 SENSOR

SIGNAL 1412 G/Y OXYGEN SENSOR 450

mv (4) 63, 64, 65 NO “CLOSED LOOP”

OPERATION (9).

D14 RH O2 SENSOR

EARTH 1413 GY/ B OXY G E N S ENSOR AND

ENGINE EARTH * * 63, 64 NO “CLOSED LOOP”

OPERATION (8).

D15 LH O2 SENSOR

SIGNAL 412 V OXYGEN SENSOR 450

mv (4) 13, 44, 45 NO “CLOSED LOOP”

OPERATION (9).

D16 LH O2 SENSOR

EARTH 413 VB OXYGEN SENSOR A ND

ENGINE EARTH * * 13, 44 NO “CLOSED LOOP”

OPERATION (8).

(1)

(4)

(9)

(10)

VARIES FROM 0.10 TO ABOUT 8.5V, DEPENDING ON POSITION OF DRIVE WHEELS WHEN VEHICLE IS MOVING.

VOLTAGE SHOULD VARY BETWEE N 100mV - 1000 mV.

OPEN/EARTHED CIRCUIT.

EARTHED CIRCUIT.

LESS THA N 0. 50 V OLT.

REFER T O WIRING DI AGRAMS.

PCM CONNECTOR E

POWERTRAIN CONTROL MODULE CONNECTOR “E” SYMPTOMS TABLE

BLUE 32 PIN E - F CONNECTOR

CKT

WIRE

COMPONENT/ NORMAL

VOLTAGES

DTCS

POSSIBLE SYMPTOMS

FROM

PIN FUNCT ION # COLOUR CONNECTOR CAVITY IG N

“ON” ENG

RUN AFFECTED FAULTY CIRCUIT

E1 BOOST

CONTROL

SOLENOID

429 B/O BOOST CONTROL

SOLENOID T E RMOI NA L

“B”

12 13 NONE FULL BOOST, BOOST

SYSTEM INOP.

E2 FUEL INJECTOR

#3 CONTROL 843 V FUEL INJ ECTOR #3 12 13 NONE ROUGH IDLE, HARD TO

START.

E3 FUEL INJECTOR

#2 CONTROL 842 G FUE L INJECTOR #2 12 13 NONE ROUGH IDLE, HARD TO

START.

E4 FUEL INJECTOR

#5 CONTROL 845 GY FUEL INJECTOR #5 12 13 NONE ROUGH IDLE, HARD TO

START.

E5 FUEL PUMP

CONTROL

MODULE (PWM)

DRFIVER

411 LT BLU FUEL PUMP CONTROL

MODULE TERMINA L “6” * 3.0 TO

3.4 v NONE POOR PERFORMANCE.

E6 PRNDL “A” 771 BLU/W PRNDL SWITCH

TERMINAL “A’ * * NONE IMPROPER GEAR

INDICA T E D ON

INSTRUMENT PANEL (9).

E7 PRNDL “B” 772 Y PRNDL SWI T CH

TERMINAL “D’ 12 13 NONE IMPROPER GEAR

INDICA T E D ON

INSTRUMENT PANEL (9).

E8 PRNDL “C” 773 GY PRNDL SWI T CH

TERMINAL “B’ 12 13 NONE IMPROPER GEAR

INDICA T E D ON

INSTRUMENT PANEL (9).

E9 NOT USED - - - - - - -

E10 NOT USED - - - - - - -

E11 NOT USED - - - - - - -

E12 OIL PRESSURE

INPUT SIGNAL 31 BLU OIL PRESSURE

SWITCH * 13 NONE OIL LIGHT ON.

E13 NOT USED - - - - - - -

E14 PRESSURE

CONTROL

SOLENOID LOW

1229 GY/BLU TRANSMISSION PASS-

THRU CONNECTOR “D”,

PRESSURE CONTROL

SOLENOID “B”

* 6.8 73 (8) MA XIMUM LINE

PRES S URE, HARD

SHIFT.

E15 PRESSURE

CONTROL

SOLENOID HIGH

1228 R TRANSMISSION PASS-

THRU CONNECTOR “C”,

PRESSURE CONTROL

SOLENOID “A”

1.1 1.3 73 MAXIMUM LINE

PRES S URE, HARD

SHIFT.

E16 ECT/TP SENSOR

EARTH 452 B/Y ECT SENSOR “B”

TP SENSOR “B”

* * 15, 21(8) HARD START, HIGH

IDLE.

(2)

(3)

(6)

(7)

(8)

(9)

12 VOLTS WHILE ENGINE IS CRANKING. LESS THAN 0.05 VOLTS WHEN STARTER IS NOT OPERATING.

WITH A I R CONDITIONI NG “ON” 0 V O LT S , WITH A IR CONDITIO NING “OFF” 13 VOLTS.

VARIES WITH TEMPERATURE.

WITH ENGINE COOLING FAN “ON” 0 VOLTS, WITH ENGINE COOLI NG FA N “OFF” 13 V OLTS.

OPEN.

OPEN/EARTHED.

LESS THA N 0. 50 V OLT.

REFER T O WIRING DI AGRAM.

PCM CONNECTOR F

POWERTRAIN CONTROL MODULE CONNECTOR “F” SYMPTOMS TABLE

BLUE 32 PIN E - F CONNECTOR

CKT

WIRE

COMPONENT/ NORMAL

VOLTAGES

DTCS

POSSIBLE SYMPTOMS

FROM

PIN FUNCT ION # COLOUR CONNECTOR CAVITY IG N

“ON” ENG

RUN AFFECTED FAULTY CIRCUIT

F1 FUEL INJECTOR

#4 CONTROL 844 BR/Y FUEL INJ ECTION #4 12 13 NONE ROUGH IDLE, HARD TO

START.

F2 FUEL INJECTOR

#1 CONTROL 841 BLU FUEL INJECTOR #1 12 13 NONE ROUGH IDLE , HARD TO

START.

F3 FUEL INJECTOR

#6 846 Y FUEL INJE CTOR #6 12 13 NONE ROUGH IDLE, HARD TO

START.

F4 A/C RELAY

CONTROL 356 LG/B A /C RELAY “1” 12 (3) NONE ROUGH IDLE, NO AIR

CONDITIONING.

F5 START RELAY

CONTROL 1434 GY/BLU START RE LA Y “86” * * 91 NO START.

F6 ENGINE

COOLING FAN

RELAY HIGH

SPEED

CONTROL

304 BLU/W COOLI NG FA N RELAY

“86” 12 (7) NONE HIGH ENGINE

TEMPERATURE

OVERHEATING.

F7 TORQUE

ACHIEVED 1427 B/W ABS/TCS MODULE “27” .9 3.6 - -

F8 NOT USED - - - - - - -

F9 RANGE SIGNAL

“A” 1224 BR/Y TRANSMISSION PASS-

THRU CONNECTOR “N”

AND PRESSURE

SW ITCH ASSEMBLY “C”

12 13 28 MAXIMUM LINE

PRESSURE, NO

FOURTH GEAR IF IN

HOT MODE, NO TCC

OPERATION.

F10 RANGE SIGNAL

“B” 1225 Y TRANSMISSION PASS-

THRU CONNECTOR “R”

AND PRESSURE

SW ITCH ASSEMBLY “E”

0 0 27

(8) NONE.

F11 RANGE SIGNAL

“C” 1226 GY TRANSMISSION PASS-

THR CONNECTOR “P ”

AND PRESSURE

SW ITCH ASSEMBLY “D”

12 13 28

(8)

MAXIMUM L INE

PRESSURE, NO

FOURTH GEAR IF IN

HOT MODE, NO TCC

OPERATION.

F12 POWER/

ECONOMY

SWITCH

774 BLU NORMAL/POWER

SWITCH 12 13 NONE NO POWER SHIF T I NG.

F13 NOT USED - - - - - - -

F14 DIAGNOSTIC

TEST ENABLE 451 W/B DLC “6) 12 13 NONE W ILL NOT FLASH DTC

12 (8).

F15 P RNDL P 776 W P RNDL S WITCH

TERMINAL “C” * * - IMPROPER GEAR

INDICA T E D ON

INSTRUMENT PANEL (9).

F16 IAT, TFT, AC

REGRIGERANT

PRESSURE

SENSOR EARTH

469 B IAT S E NSOR “B”

TFT SENSOR “B”

PRESSURE SENSOR

“A”

* * 23, 59,

(8)

SLIGHT HIGH IDLE TCC

APPLY EARLY.

(2)

(3)

(6)

(7)

(8)

12 VOLTS WHILE ENGINE IS CRANKING. LESS THAN 0.05 VOLTS WHEN STARTER IS NOT OPERATING.

WITH A I R CONDITIONI NG “ON” 0 V O LT S , WITH A IR CONDITIO NING “OFF” 13 VOLTS.

VARIES WITH TEMPERATURE.

WITH ENGINE COOLING FAN “ON” 0 VOLTS, WITH ENGINE COOLI NG FA N “OFF” 13 V OLTS.

OPEN.

LESS THA N 0. 50 V OLT.

REFER T O WIRING DI AGRAM.

TESTING EARTHS

Unusual displays in the instrument cluster, lamps

that are dim or flash unexpectedly, unexpected

readings - gremlins? Probably not; these are

classic symptoms of earth problems.

This section discusses the importance of good

earth circuits. It starts by explaining some basic

theories. Then, you are shown how to diagnose a

solid-state circuit earth condition and how, if there

is a problem, to correct it.

BASICS

For a circuit to operate properly, you need three

things - a good power supply to components, good

components, and good earths. Circuits are

complete systems; current must flow from

beginning to end as designed, not hindered by

unexpected resistance anywhere in the circuit.

Some tec hnic ians r ealis e that the power supply to a

circuit must be free of unwanted resistance, but

have difficulty visualising why an earth circuit must

also be f r ee of unwanted res istanc e. Curr ent f low is

through a complete circuit; it passes through and

out of a component like water flowing through a

tub. With a properly draining tub (no clogs), the

water can flow out as freely as it flow in. Current

mus t enter and leave c om ponents f reely, if they are

to perform as designed.

4289

Figure 6C1-2B-2

1. Voltage = Resistance X Current V = R X I

2. Resistance = Current Relationship With Fixed Voltage

3. Large Resistance, Small Current

4. Small Resistance, Large Current

Sensitive solid-state systems have their own earths;

high cur rent devices (like m otors) do not earth at the

same location. High current devices can cause

voltage spikes (sudden changes in voltage) when

turned "ON" or "OFF." To prevent these spikes from

affecting sensitive solid-state circuits, the two

different types of systems use different earth

locations. The use of a dedicated wire to connect an

isolated earth junction block to the battery negative

terminal. This wire reduces the effect of spikes on

sensitive circuits at the earth junction block.

Solid-state circuits are particularly sensitive to poor

circuit c ontinuity becaus e in mos t cases they use low

current f low. This sec tion on earth concerns with one

solid-state device, the PCM. However, the

information included here applies to all solid-state

earth circuits.

Severe restrictions in the earth circuit can cause

resets and intermittent codes in solid-state systems.

The PCM operates devices (fuel injectors, idle air

control, etc.) and receives inputs from low voltage

sensors, manifold absolute pressure sensor,

crankshaft speed/position. These input and output

devices need good circuitry for correct operation.

Remember, that when misadjusted or imperfect

sensors cause values to shift there are usually

driveability problems. If there is excessive resistance

in the earth circ uit, the res ult will be the same; shifted

sensor outputs with corresponding driveability

conditions. These conditions may not be severe

enough to set diagnostic trouble codes, but they will

reduce vehicle efficiency and performance and may

be noticed by the customer.

Sensor circuit earth sensitivity - an example.

Looking at the Throttle Position (TP) sensor circuit

will provide an example of how a little resistance in

the earth circuit can cause problems. The

accompanying figure (Figure 6C1-2B-4) shows a

throttle position sens or first with a good earth circ uit

and then with a poor connection in the earth circuit.

Refer to this figure as you proc eed through the text

that follows.

A throttle position sensor consists of a resistor and

a wiper. One terminal of the resistor is connected to

a supply voltage and the other earth. As the wiper

moves along the resistor, the voltage of the wiper

terminal progressively changes. If the wiper is near

the supply voltage end of the resistor, the wiper

output will approach the supply voltage (over 4.5

volts at wide open throttle). As the wiper moves

toward the earthed end of the resistor the voltage

of the wiper output decreases to near zero (about

0.5 volts for the closed throttle in this example).

(The actual closed and wide open throttle voltage

specifications may vary for different engines.) The

sensor output should never be greater than

reference supply voltage or less then .20 volts.

(The PCM would set a diagnostic trouble code if

this occurs.)

The Figure 6C1-2B-4 shows voltage drops across

various points in the circuit. In the example with

good circuit earth, the T P sensor is shown with the

wiper in the closed throttle position. The total

voltage across the resistor in the TP sensor is 5

volts. The voltage drop from the resistor source

voltage terminal to the wiper is 4.5 volts. The

voltage drop from the wiper to the resistor earth

side is 0.5 volts. The wiper output is 0.5 volts - a

good value for this example of a closed throttle.

Now, look at the sens or with the bad signal caused

by resistance in the earth circuit. The throttle

positions stays the same but the sensor output

voltage changes. In this example the increased

resistanc e causes an additional voltage drop of 0.5

volts. The voltage drop from the wiper to found is

now 1.0 volt (0.5 + 0.5 = 1.0). Because the source

voltage is a constant 5 volts, the voltage drop from

the source voltage input to the wiper can now be

only 4 volts (5.0 - 1.0 = 4.0). The PCM now

receives 1.0 volt from the TP sensor. This is not a

good value (in this example) of a closed throttle

Now you can s ee why good earths are needed and

how sensitive some circuits can be.

4290

Figure 6C1-2B-3

1. Sensor With Good Earth.

2. Fixed 5 Volts.

3. Throttle Position Sensor.

4. 0.5 Volts Sensor Output.

5. Wiper.

6. Sensor With Poor Earth.

7. 1.0 Volts Sensor Output.

8. Voltage Drop Caused By Resistance of Poor Earth is 0.5

Volts.

9. Total Voltage Drop Below Wiper is 1.0 Volts.

10. Voltage Drop of 0.5 Volts.

11. Voltage Drop of 4.0 Volts.

12. Voltage Drop of 4.5 Volts.

EARTH CIRCUITS

How do you know which wires are ear th wires, which

connectors they go through, and whether they are

connected to an earth junction or the body?

Section 12P, WIRING DIAGRAMS in VX Service

Information should be used whenever you are

diagnosing any electrical condition, including earths.

The individual circuits show the power and earth

circuits for components in specific systems.

If you suspect s ever al cir cuits ar e being af f ec ted by a

poor or a back-feed to earth, look at the circuits to

see how the systems might interact. If they have any

common earth wires, that is where you should start

diagnosis.

Back-feeding is when current, seeking earth, feeds

back through inactive circuits (the reverse direction

of normal current flow) to find a path to earth. This

can only happen when the active circuit (needing an

earth) shares a disconnected or poor earth with an

inactive circuit and the voltage supply side of the

inactive circuit feeds other components with good

earths.

PARALLEL EARTHS

Some solid-state components use redundant earth

circuits; that is, they have more than one wire

connecting to earth. The PCM has more than one

earth circuit wire. There are several reasons for

redundant earths.

The PCM has many low-current circuits, but the

current from all these circuits (when they are

active) adds up to a larger current. Higher current

loads are managed more easily with several regular

size wires, rather than with one large diameter wire.

Basic circuit theory shows that the effective

resistance of parallel resistors is less than any of

the individual resistors. This is true for even the

small resistance's in wires. Parallel wires provide

the lowest resistance. Because of them, in many

solid-state systems a pr oblem with one of the earth

wires would not affect the circuit; the redundant

wires could handle the c ur rent load. F or other s olid-

state systems the loss of even one redundant ear th

may affect operation, but the remaining earth

wire(s) may allow the vehicle to be driven.

Here is one exam ple which can pr ove to be dif ficult

to a driveability technician. Sym ptom : A vehic le has

driveability symptoms. Whenever a scan tool is

hooked up and the vehicle tested, none of the

complaint symptoms are displayed.

Cause: The PCM earths are not providing a good

earth, hence the resulting driveability condition.

When a scan tool is plugged in, a good earth path

is provided for the PCM through the Data Link

Connector (DLC). The DLC uses a different earth

than the PCM. Always test for driveability

symptoms before hooking up a scan tool. If they

disappear when the scan tool is hooked up, check

the earth circuit for continuity.

The severity of the symptom(s) is proportional to

the severity of the problem in the earth circuit. A

complete open in the circuit has the most severe

effect. Use the severity of the symptom(s) as an

indication of the extent of the open in the earth

circuit.

Figure 6C1-2B-4

1 1 1 1

------ = -------- + ------ + ------- + ...

R TOTAL R 1 R 2 R 3

EXAMPLE: 2 PARALLEL CIRCUITS, ONE WITH

ONE OHM RESISTANCE AND

THE OTHER WITH TWO

OHMS RESISTANCE.

1 1 1

------ = -------- + ------

R TOTAL 11 2 2

1 2 1

------ = -------- + ------

R TOTAL 2 2

1 3

------ = --------

R TOTAL 2

R TOTAL = -------- Ω

WITH METER

NEGATIVE (BLACK)

PROBE AT THE

BATTERY NEGATIVE

TERMINAL, PLACE THE

METER POSITIVE (RED)

PROBE

MAXIMUM ALLOWABLE

VOLTAGE

BETWEEN SENSOR

AND PCM

0.060 (60 MILLIVOLTS)

BETWEEN PCM AND

BATTERY NEGATIVE

TERMINAL

0.020 (20 MILLIVOLTS)

Figure 6C-2B-5

CHECKING EARTHS

Once you determine that the caus e of the vehic le symptom (s) m ay be caused by a bad earth, It is time to c heck for

poor earth with one more tool: a high-impedance voltmeter.

The bes t way to check for poor earth connections in low-c urrent solid-s tate circuits is to check the voltage drop. To

do this you need a high-impedance voltmeter rated at a minimum of 10 megaohms (10,000,000 ohms) per volt.

Most quality digital multimeters meet or exceed this specification. Voltmeters with less impedance can affect the

circuit you are testing and also give an incorrect reading.

Start by checking the entire suspect earth circuit. With a voltmeter set on the 2 volt DC scale, connect the black

negative lead to the batter y negative terminal. ( If you are using an auto-ranging m eter , set it to the DC volts s etting.

Connect the red positive lead to the earth term inal of the com ponent to be tested. W ith the circuit ac tivated, check

the voltage drop in the circ uit. If the voltage reading is within specif ications, look f or a cause other than a poor earth

at this component.

If the voltage reading is too high, proceed by isolating the cause of the high voltage dr op. Move the positive lead to

the next connection in the ear th c irc uit. (Keep the negative lead c onnected to the battery negative terminal.) Be sure

to check both sides of each in-line connector and both the eyelet and the stud or screw at earth points. Repeat this

process through the earth path until the voltmeter reading is within specifications. The high resistance causing the

earth problem is located between where you obtained a good reading and the last high reading.

When a circuit uses redundant earths be sure to check all the earths circuits for excessive voltage drop.

SOLID-STATE CIRCUIT VOLTAGE DROP SPECIFICATIONS

There ar e two ac c eptable maximum voltage dr ops for solid- s tate cir cuits . If you are meas ur ing the voltage drop of a

circuit that will pass through a solid-s tate com ponent bef ore going to earth ( such as the ECT sensor circ uit between

the ECT sensor and the PCM), measured voltage cannot be higher than 0.060 volts (60 millivolts).

If you are measuring the voltage drop of a solid-state earth circuit anywhere in the earth path at or after the solid-

state component (such as the PCM earth circuit from the PCM to the battery), the maximum allowable measured

voltage is 0.020 volts (20 millivolts). If you measure a voltage above specifications, repair the earth circuit.

Checking the voltage drop in a solid-state sensor circuit - an example. Look again at a throttle position sensor

circuit. W ith the voltmeter negative lead connected to the negative battery terminal and the ignition in RUN, check

the voltages at various points between the ECT sensor pin "B" and pin "E16" of the PCM. A voltage reading of 0.060

volts or less with the meter positive lead at the ECT sensor pin "B" terminal indicates that the entire earth circuit

from the ECT sensor to the battery is continuous and s uffic iently low in resistanc e. A voltage reading of 0.060 volts

at "the splice" or the PCM connector "E16" pin would also be within specifications.

When voltage measurements are made in the earth circuit after the PCM, the specification changes. A voltage

reading of 0.020 volts (20 millivolts) or less is within specification. If voltage is not within specifications check the

diff erent connectors to find where the exces s voltage is. Be sure to c heck both s ides of in-line c onnectors and both

the eyelet and the stud at earth points.

Figure 6C1-2B-6 Testing Voltage Drop Before the PCM

1. Throttle Position Sensor. 2. Engine Coolant Temperature Sensor. 3. PCM.

4. Sensor Return. 5. Red Lead. 6. Black Lead.

7. Battery 8. 0.60 Volts Maxium.

Figure 6C1-2B-7 Testing Voltage Drop After the PCM

1. Earth. 2. PCM. 3. Oxygen Sensor. 4. Red Lead.

5. Black Lead 6. Battery 7. 0.020 Volts Maxium.

4291

111

4292

EARTH CREDIBILITY HE CK

Circuit Description:

The earth credibility check can be either used at the beginning of all diagnostic procedures or it c an be used when

no diagnostic trouble codes are set, but a sy mptom still exists.

Test Description:

Number(s) below refer to step number(s) on the diagnostic Table.

1. To properly test the voltage drop of the powertrain control module system earth a load must be present on

the circuit.

Using the scan tool:, select CANISTER PURGE. By turning "ON" the Purge solenoid, this will cause a

sufficient draw on the system for testing.

2. Check connectors in earth circuit to f ind where the excessive voltage is. Mak e sure to check both sides of

in-line connectors.

Diagnostic Aids:

Because the powertrain control m odule operates on such sm all current even a minor corrosion problem will cause

problems with the system. Make sure the earths are clean and tight. Rem ember a good earth is about 25% of the

total systems circuit. Normally you will check the wiring for: power, continuity, the load, but rarely check the earth.

Powertrain control module system earths are very important to proper operation.

AIR TEMP SENS OR

YE 23

(469)

(472)

LOCATION E3 EARTH CONNECTOR

RIGHT HAND INNER FENDER

YE114

(151)

B/G

(157)

B/R

(150) (155)

BB/Y

(152)

B/W

(157)

B/R

SUPERVX002

F16

INTAKE AIR

TEMPERATURE SENSOR

SENSOR EARTH

IAT SENSOR SIGNAL

PCM

BR (472)

B (46 9 )

A/C PRESSURE

SENSOR AND

TFT SENSOR

YE23 YB188

YB194

EARTH CREDIBILITY CHECK

STEP ACTION VALUE YES NO

1. Was the "On-Board Diagnostic" (OBD) System Check

performed? Go to Step 2. Go to OBD

System Check.

2. 1. Ignition "OFF"

2. Disconnect IAT sensor connector.

3. Using digital volt ohm meter set to DC voltage scale,

connect negative lead to negative battery cable at

battery and connect positive lead to the black wire at

the IAT sensor connector.

4. Ignition "ON"

5. Using a scan tool, select CANISTER PURGE.

6. Turn "ON'" Canister Purge with up/down arrow keys.

Is voltage measured less than value shown.

0.060 volts

(60 Millivolts) No problem

found, continue

with symptom

diagnosis.

Go to Step 3

3. 1. Remove and thoroughly clean the PCM earth

terminals and connection.

2. Reassemble the PCM Earth terminals.

Is action complete?

Verify Repair

CORRECTING PROBLEMS IN EARTH CIRCUITS

Once a high resistance condition in a earth circuit has been located, you must determine the actual cause.

If the problem is at a connector, check for bent, corroded, or loose connector term inals. Term inals must have a

slight drag when disassembled/assembled. If they slide apart/together without resistance, they will not provide a

good connection.

If the prob lem is at a st ud , bolt, or sheet metal screw, check for corrosion, paint, or loose connections. Paint can

be a very good insulator; good conductors, not insulators are needed for electrical connections.

Corrosion, paint, and other contaminants should be removed using a wire brush and/or emery cloth.

When assembling earth wire eyelet's on earth points, be sure an external type star washer is placed below the

wire eyelet(s). If the system is marginal, you can also place a st ar washer between the nut or the sheet- metal sc rew

and the top wire eyelet. Tighten the fastener to specification, making sure the star washer digs through any paint

into the mounting surface. Star washers also lock the fastener in place, preventing it from loosening.

All fasteners should be tightened so that the fastener head presses the earth wire eyelet or star washer to the

mounting surface and stops. Repair any stripped earth fasteners.

IMPORTANT

Do not over-tighten sheet-metal screws. Over-tightening can enlarge the hole and create a bad earth. If the sheet-

metal is enlarged, the screw will continue to turn: drill a new correctly sized hole for the screw.