INFO ON SHIFT INDICATOR LIGHT APPLICATION AND OPERATION

SUBJECT: INFORMATION ON SHIFT INDICATOR LIGHT APPLICATION AND OPERATION

VEHICLES AFFECTED: 1992 C, K, P TRUCKS WITH 4.3L ENGINE (VIN Z) AND MANUAL TRANSMISSION

Certain 1992 C, K and P trucks with 4.3L engines (VIN Z/RPO LB4) do not make use of a shift indicator light:

- The shift light is commonly used to achieve improved fuel economy, by prompting the driver to upshift.

Depending on which prom calibration is installed in the ECM/PCM, the shift light can have the following characteristics:

- Indicates proper shift point for maximum fuel economy. - Indicates engine over-rev (above 4000 rpm). - Shift light is inoperative.

Use following Chart to determine normal shift light operation for the vehicle in question:

FUEL ECONOMY OVER REV GVW SERIES TRANS RPO SHIFT LIGHT SHIFT LIGHT --- ------ --------- ------------ ----------- (8500 GVW C MG5 YES YES (8500 GVW C MT8 NO YES (8500 GVW K MG5 NO YES (8500 GVW K MT8 NO YES OVER 8500 GVW C,K,P MT8 NO NO OVER 8500 GVW C,K,P M20 NO NO

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.