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Contents

Section: Diagnosis - A/t

THM 3T40 APPLICATION

THM 4L60/700-R4 APPLICATION (1991-92)

THM 4T60 & 4T60-E APPLICATION (1991-92)

THM 4L80-E APPLICATION

THM 4L80-E SERIES CODE DESIGNATION

MP6 & MP7 APPLICATIONS (1991-92)

DIAGNOSTIC FLOW

DESCRIPTION

TCC CONTROL COMPONENTS

Brake Switch

Coolant Temperature Sensor

Electronic Control Module (ECM)

TCC Solenoid Assembly

Throttle Position Sensor (TPS)

Vacuum Sensor

Vehicle Speed Sensor (VSS)

3rd & 4th Gear Switches

TROUBLE SHOOTING

Problem In Electronic Control Module

Electrical Problems

Valve Body Assembly

Oil Pump Assembly

CONVERTER CLUTCH APPLY SLIPS, ROUGH OR SHUDDERS

CONVERTER CLUTCH DOES NOT RELEASE

DIAGNOSTIC TOOLS

RETRIEVING TROUBLE CODES

CLEARING TROUBLE CODES (EXCEPT SATURN)

CLEARING TROUBLE CODES (SATURN)

ENTERING SELF-DIAGNOSTICS

EXITING SELF-DIAGNOSTICS

DISPLAYING TROUBLE CODES

CLEARING TROUBLE CODES

SYSTEM SELECTION

TEST TYPE SELECTION

CLEAR CODES

DATA

INPUTS

OUTPUTS

OVERRIDE

SNAPSHOT

EXPLANATION OF SPECIFIC TEST SELECTION

SPECIFIC TEST SELECTION

BCM Snapshot

ECM Snapshot

STATUS LIGHT INDICATORS

ECM

HIGH

MED

LOW

OFF or VENT

Left-Side AUTO

°C

Upper Arrow (Icon)

BCM

Lower Arrow (Icon)

TCC LOCK-UP PROBLEMS

NO LOCK-UP CONDITION

BRAKE SWITCH TEST

CHECKING SELF-DIAGNOSTIC SYSTEM

TCC APPLY SOLENOID TEST

NO TCC RELEASE CONDITION

CHECKING VOLTAGE TO TERMINAL "A" AT TRANSMISSION USING ALDL

CHECKING VOLTAGE TO TERMINAL "A" AT TRANSMISSION

CHECKING FOR GROUND AT TERMINAL "D" AT TRANS. USING ALDL

CHECKING FOR GROUND AT TERMINAL "D" AT TRANSMISSION

COOLER LINE PRESSURE TEST

ELECTRICAL SWITCHES TEST

Single Terminal Switch (8642473) & 2 Terminal Switch

Single Terminal Switch (8642569 & 8634475) & 2 Terminal

GROUNDING "D" WIRE AT TRANSMISSION USING ALDL

SELF-DIAGNOSTIC SYSTEM CHECK REATTA & RIVIERA

Always Start Electrical Or Electronic Diagnosis Here

Diagnostic Aids

CHART A-2, SERVICE ENGINE SOON LIGHT WON'T GO OUT OR FLASH (REATTA & RIVIERA)

CHART B-1, BCM POWER & GROUNDS - REATTA & RIVIERA

CHART C, ECCP DISPLAY PROBLEMS (LOSS OF ECCP COMMUNICATIONS) (REATTA & RIVIERA)

CHART D-2, SERIAL DATA CIRCUIT SHORTED TO VOLTAGE - REATTA & RIVIERA

CHART A-2, SERVICE ENGINE SOON LIGHT WILL NOT GO OUT OR FLASH - TORONADO & TROFEO

SELF-DIAGNOSTIC SYSTEM CHECK (NON-CRT TORONADO & TROFEO)

CHART C, LOSS OF ECCP COMMUNICATIONS (NON-CRT EQUIPPED TORONADO & TROFEO)

CHART D, LOSS OF COMMUNICATIONS (NON-CRT EQUIPPED TORONADO & TROFEO)

CHART D-2, SERIAL DATA CIRCUIT SHORTED TO VOLTAGE (NON-CRT EQUIPPED TORONADO & TROFEO)

CHART C, COLOR CRT UNABLE TO CONTROL ECCP (CRT EQUIPPED TORONADO & TROFEO)

CHART D, SERIAL DATA CIRCUIT OPEN (CRT EQUIPPED TORONADO & TROFEO)

CHART D-1, GROUNDED SERIAL DATA CIRCUIT (CRT EQUIPPED TORONADO & TROFEO)

CHART E, COLOR CRT ABNORMALITIES (CRT EQUIPPED TORONADO & TROFEO)

Note On Intermittents

CODE 23, MAT SENSOR SIGNAL VOLTAGE HIGH

CODE 26, DIAGNOSTIC CIRCUIT CHECK

SERVICE ENGINE SOON LIGHT INOPERATIVE

SERVICE ENGINE SOON LIGHT WON'T GO OUT OR FLASH CODE 12

Hot Light Diagnosis

QDM CIRCUITS

Hot Light Diagnosis (C Body)

CODE 27 OR 28, GEAR SWITCH CIRCUITS - 3.3L WITH 3T40 TRANSAXLE

CODE 28 OR 29, GEAR SWITCH CIRCUITS - 3.3L A BODY WITH 4T60

CODE 31, PARK/NEUTRAL SWITCH CIRCUIT - 3.3L & 3.8L

Poor Connection or Damaged Harness

Intermittent Test

CODE 39, TCC CIRCUIT 3.3L WITH 3T40 TRANSAXLE

CODE 39, TCC CIRCUIT 3.3L & 3.8L WITH 4T60 (440-T4) TRANSAXLE

CHART C-8, TORQUE CONVERTER CLUTCH ELECTRICAL DIAGNOSIS - 3.1L PFI A & J BODIES (2 OF 2)

1st Gear

2nd Gear

3rd Gear

CHART C-8C, 4T60 TRANSAXLE 1ST GEAR SWITCH ELECTRICAL DIAGNOSIS - 3.4L PFI W BODY

CHART C-8B, 4T60 TRANSAXLE SHIFT SOLENOID FUNCTIONAL CHECK - 1991 E BODY (EXCEPT ELDORADO) 3.8L PFI (VIN L)

Transaxle Prefunctional Check

No Indicator Lights On Or Ignition Indicator Light Only On

Battery Indicator Light On, All Other Indicator Lights Off

Brake Indicator Light Not On

Shift "A" And/Or Shift "B" Indicator lights Not On

Converter Clutch Apply Indicator Light On All The Time

Converter Clutch MOD Indicator Light On All the Time

CHART C-8B, 4T60 TRANSAXLE SHIFT SOLENOID FUNCTIONAL CHECK - 3.8L PFI (VIN L & 1) 1992

CHART C-8A, TORQUE CONVERTER CLUTCH FUNCTIONAL CHECK - 1992 3.8L PFI (VIN 1)

CHART C-8B, 4T60 TRANSAXLE SHIFT SOLENOID FUNCTIONAL CHECK - 1992 3.8L PFI (VIN 1)

Diagnostics Aids

CODE 23, MAT SENSOR TEMP. LOW - 1991 2.5L & 4.3L TURBO

CODE 25, MAT SENSOR TEMP. HIGH - 1991 2.5L & 4.3L TURBO

CODE 25, MAT SENSOR TEMP. HIGH - 1992 2.5L & 4.3L TURBO

CODE 53, SYSTEM VOLTAGE HIGH - LT. TRUCK

Notes On Intermittents

CODE 59, TRANSMISSION TEMPERATURE SENSOR CIRCUIT (LOW TEMPERATURE INDICATED) - LT. TRUCK

CODE 75, SYSTEM VOLTAGE LOW - LT. TRUCK

CODE 83, TCC QDM FAULT - LT. TRUCK

CODE 86, SHIFT SOLENOID "B" STUCK "ON" - LT. TRUCK

CODE 87, SHIFT SOLENOID "B" STUCK "OFF" - LT. TRUCK

TORQUE CONVERTER CLUTCH CIRCUIT CHECK - LT. TRUCK

SHIFT SOLENOID "A" CIRCUIT CHECK - LT. TRUCK

SHIFT SOLENOID "B" CIRCUIT CHECK - LT. TRUCK

FORCE MOTOR CIRCUIT CHECK (LT. TRUCK)

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EXITING SELF-DIAGNOSTICS GMC Sonoma Syclone

Diagnosis - A/t

EXITING SELF-DIAGNOSTICS

During self-diagnostics procedure, it is possible to exit service mode without erasing trouble codes. On non-CRT equipped vehicles, depress BI-LEV button on ECCP or turn ignition switch to OFF position. On CRT monitor equipped panel vehicles, touch RTN key on CRT monitor panel or turn ignition switch to OFF position.