NO UPSHIFT/STUCK IN FIRST/NO CODES/EXTERIOR LEAKS

SUBJECT: NO UPSHIFT/STUCK IN FIRST/NO CODES/EXTERIOR LEAKS (REPLACE SPEED SENSOR)

MODELS: 1991-93 C/K, RIV, P, AND G VEHICLES WITH 4L80-E/4L80-EHD TRANSMISSIONS

CONDITION

Some 1991-93 C/K, R/V, P, and G Vehicles With 4L8O-E/4L80-EHD transmissions may experience a no upshift, stuck in first with no Diagnostic Trouble Codes (DTC) stored.

CAUSE

Input/output speed sensor malfunction, or leaking (wicking) fluid through the speed sensor connector (internal and/or external). If the input speed sensor is not functioning correctly, the output speed sensor is not used for reference by the PCM/TCM and an upshift cannot occur.

CORRECTION

Diagnose per the input speed sensor circuit check as outlined in Section 7A of the appropriate service manual. Replace the speed sensor if necessary.

DATE OF PRODUCTION: (Figure 1)

Starting January 15, 1993 (Julian Date 015) all 1993 C/K, R/V, P, and G Vehicles With 4L80-E/4L80-EHD transmissions will have the new speed sensor assemblies.

SERVICE PARTS INFORMATION

Part # Description 8685042 Speed Sensor Assembly

WARRANTY INFORMATION

For vehicles repaired under warranty, use:

Labor Codes: Replace input sensor K6311 or output sensor K6312.

Parts are expected to be available on March 22, 1993.

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.