A/T - Loss of Drive or Erratic Shifts
Group Ref.: 7 - TransmissionBulletin No.: 477121
Date: August, 1994
SUBJECT:
INTERMITTENT LOSS OF DRIVE OR ERRATIC SHIFTS
(DIAGNOSIS FOR ELECTRICAL CONDITION)
MODELS:
1991 BUICK REATTA
1991-1993 BUICK RIVIERA
1991-1994 BUICK PARK AVENUE AND REGAL
1992-1994 BUICK LE SABRE
1994 BUICK CENTURY AND SKYLARK
1991-1993 CADILLAC ELDORADO, SEVILLE, SIXTY SPECIAL AND
FLEETWOOD (FWD)
1991-1994 CADILLAC DE VILLE
1991-1994 CHEVROLET LUMINA
1992-1994 CHEVROLET LUMINA APV
1994 CHEVROLET BERETTA AND CORSICA
1991-1992 OLDSMOBILE TORONADO AND TROFEO
1991-1994 OLDSMOBILE NINETY EIGHT AND CUTLASS SUPREME
1992-1994 OLDSMOBILE EIGHTY EIGHT AND SILHOUETTE
1994 OLDSMOBILE CUTLASS CIERA AND ACHIEVA
1991-1994 PONTIAC GRAND PRIX
1992-1994 PONTIAC BONNEVILLE AND TRANS SPORT
1994 PONTIAC GRAND AM
TRANSAXLE APPLICATIONS:
HYDRA-MATIC 4T60-E (RPO M13)
CONDITION:
Some owners may experience one or more of the following intermittent conditions:
^ Loss of drive (neutral condition) on highway while in fourth gear.
^ Erratic upshifts and downshifts at steady throttle angles without a Malfunction Indicator Light (MIL) (Service Engine Soon) illuminated.
^ First and second gear only (no third or fourth gear).
^ First and fourth gear only (no second and third gear).
CAUSE:
These intermittent conditions may be caused by an intermittent short to ground on the "A" or "B" Shift Solenoid wiring between the ECM/PCM and the transaxle or an internal electrical condition in the transaxle. In most cases, these conditions ARE NOT caused by a hydraulic or mechanical condition in the transaxle.
CORRECTION:
To diagnose this condition, it will be necessary to perform the following steps that are covered in detail under "Service Information":
1. Check condition and level of transmission fluid.
2. Diagnose and repair all ECM/PCM Diagnostic Trouble Codes.
3. Identify which shift solenoid is being affected.
4. Determine if cause is internal or external to transaxle.
5. Identify faulty component and repair or replace as necessary.
SERVICE INFORMATION:
1. Check condition and level of transmission fluid
Use the "4T60-E Transaxle Fluid Checking Procedure" in Section 7A-5A 4T60-E AUTOMATIC TRANSAXLE DIAGNOSIS of the appropriate Service Manual. If the fluid is contaminated, burned or contains excessive clutch material or metal, this bulletin no longer applies and mechanical/hydraulic diagnosis should be followed per the Service Manual.
2. Diagnose and repair all ECM/PCM Diagnostic Trouble Codes
Check for ECM/PCM DTC's using the TECH 1/0n-board Diagnostics as described in Section 6E-A of the appropriate Service Manual. Diagnose and repair all DTC's prior to continuing to step three.
3. Identify which shift solenoid is being affected
Install the Transmission Test Box J 38791 and the correct harness (J 38791-10, J 38791-20 or J 38791-60) and monitor "A" and "B" Shift Solenoid LED status during condition. Compare the actual LED status with the commanded gear status indicated by the TECH 1. The Shift Solenoid that is energized when it is not commanded to be energized is the affected component. (On Pontiac models, use Transaxle Electrical Jumper J 38835 and Multimeter J 39200.)
4. Determine if cause is internal or external to transaxle
If the condition can be eliminated or changed by manually overriding the selected gear with the Transmission Test Box, then the electrical fault is external to the transaxle. If the condition cannot be eliminated using the Test Box, then the fault is internal to the transaxle. It is possible with some Shift Solenoid conditions that the affected solenoid will behave as if it was energized (check ball seats) without actually being energized. In this case, the TECH 1 commanded status and Transmission Test Box LED status will be the same and the condition will not be affected by the Test Box.
5. Identify faulty component and repair or replace as necessary
Once the fault has been identified as internal or external to the transaxle and one Shift Solenoid is affected, the following suggestions will help to identify the exact component and required repair:
Wiring faults external to the transaxle:
^ Check for pinched wiring or worn through insulation underhood at exposed sheet metal, harness retainers or at pass-through connectors at the cowl. Underdash wiring as it routes to the ECM/PCM could also be damaged.
^ If the condition occurs during powertrain torque loads (acceleration), check for harnesses that are pulled tight against a component when the powertrain moves fore or aft.
^ Check any pass-through or in-line harness connectors for bent or damaged terminals.
^ Repair damaged wiring and repair or replace terminals and connectors per Section 8A-5 of the appropriate Service Manual.
^ On 1991-1993 Cadillac DeVille/Fleetwood/Sixty Special (FWD) models, refer to Cadillac bulletin T-93-105 or Canada bulletin 93-6E-125 (Corporate bulletin 316510).
Wiring faults internal to the transaxle:
^ Check for wiring pinched between the side cover and channel plate/valve body.
^ Check for bent or damaged connector pins.
^ Check suspect Shift Solenoid for high/low resistance using nominal readings from Section 7A-5A 4T60-E AUTOMATIC TRANSAXLE DIAGNOSIS in the appropriate Service Manual.
^ The transaxle Wiring Harness or Shift Solenoid must be replaced if faulty; they are not currently repairable.
Non-electrical Shift Solenoid faults:
^ Check for sediment in Shift Solenoid.
^ Check for sediment, broken/missing spring, or binding valve in shift valve train.
^ The transaxle Shift Solenoid must be replaced if faulty; it is currently not repairable.
SERVICE PARTS INFORMATION:
If a component requires replacement, refer to the Service Parts Catalog for part numbers.
WARRANTY INFORMATION:
For vehicles repaired under warranty, use the appropriate labor operation and its published time from the list: