GM Service Manual Online
For 1990-2009 cars only

TEMPERATURE GAUGE READS HIGH UNDER NORMAL DRIVING CONDITION

SUBJECT: INDICATED OVERHEAT CONDITION (REPLACE SENSOR)

VEHICLES AFFECTED: 1990-91 U-VAN

Condition:

----------- The engine temperature gauge may read high (into the red zone) under normal driving conditions.

Cause:

-------- An improper material in the tip of the temperature sensor can cause the temperature gage to read too high. The sensor was changed in production with VIN MT119675 (Chevrolet), MT210327 (Pontiac), and MT305067 (Oldsmobile).

Correction:

------------ Verify that the engine does not have a true overheat condition by comparing the temperature reading of the ECM coolant sensor (measured with a SCAN tool) to the gauge reading. If the ECM sensor reads normal at the same time the temperature gage reads high, replace the temperature sensor with P/N 10200490.

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.