ERRATIC/NO SPEEDOMETER/TRANS OPERATION

SUBJECT: ERRATIC/NO SPEEDOMETER OPERATION AND ERRATIC TRANSAXLE SHIFT OPERATION WITH PCM CODE E24/E024 OR E75/E075

MODELS AFFECTED: 1991 DE VILLES, FLEETWOODS, EL-DORADOS, AND SEVILLES

Some 1991 DeVilles, Fleetwoods, Eldorados, and Sevilles equipped with a 4T60-E transaxle may experience erratic transaxle shift operation along with erratic/no speedometer operation due to an erratic or inoperative Vehicle Speed Sensor (VSS). VSS conditions will also cause Powertrain Control Module (PCM) codes E24/E024 and or E75/E075 to set.

An erratic VSS may function normally when cold and perform erratically as the vehicle is brought up to operating temperatures.

When the PCM detects a VSS fault, the PCM will force the transaxle into second gear under most conditions. This "fail safe" second gear operation may cause customer comments that the vehicle is sluggish or slips.

When servicing vehicles for the above conditions, start with code E24/E024 and E75/E075 diagnosis from the 1991 New Product Information (NPI) manual. If the VSS is confirmed as the fault, or no trouble found at this time is indicated, replace the VSS with P/N 10456034 per procedures listed in Section 7Al of the NPI manual.

Parts are currently available from GMSPO.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.