A/T Speed Sensor - Erratic Shifts/No Speedometer

90pontiac25
Bulletin Number: 91-7-16
Reference Number: 077142
Publish Date: 11/90
Subject: ERRATIC/NO SPEEDOMETER AND ERRATIC (TRANS OPERATION W/CODE 24 (SPEED SENSOR)

Models

Affected: 1991 GRAND PRIX MODELS W/4T60E 3.4L TWIN DOHC ENGINE
BULLETIN COVERS:

A vehicle equipped with a HYDRA-MATIC 4T60-E may exhibit erratic or no speedometer reading and erratic transaxle operation. This will be accompanied by code 24. These conditions could be caused by an inoperative transaxle speed sensor. When the powertrain control module (PCM) detects an inoperative speed sensor, the PCM will force the transaxle into fail-safe 3rd gear. Fail-safe 2nd or 3rd gear operation may cause customer comments that the vehicle is sluggish or slips. Also, an intermittent speed sensor condition may result in normal operation when cold, and when the vehicle is brought up to operating temperature, erratic operation of the speedometer and transaxle.

SERVICE PROCEDURE:

Replace the transaxle speed sensor with the part listed under "SERVICE PARTS INFORMATION".

SERVICE PARTS INFORMATION:

Part Number Description Model Usage

10456034 Speed Sensor Assembly All

Parts are currently available from GMSPO.

SERVICE MANUAL REFERENCE:

Refer to 1991 Service Manual On-Car section for prover disassembly and assembly procedures.