GM Service Manual Online
For 1990-2009 cars only

The instrument cluster controls headlamp systems that include Daytime Running Lamps (DRL). The system allows the headlamps to operate at a reduced intensity when all of the following conditions apply:

    • The engine is running.
    • The transaxle is not in the PARK position.
    • The normal headlamps are not on.

The instrument cluster turns the DRL system on by grounding circuit 592, thereby energizing the DRL relay. This action allows a reduced voltage of 6 volts to flow across the headlamps. If the vehicle has the optional fog lamps, the fog lamp relay will also be energized. The park lamps will turn on and the fog lamps will operate normally. When the headlamp switch is turned to the ON position, the instrument cluster allows normal headlamp operation.

The instrument cluster also has an input from the park brake. If the park brake is in the ON position, the DRL will remain disabled until the park brake is placed into the OFF position. On vehicles with an automatic transaxle, the instrument cluster will disable the DRL until the transaxle has been taken out of the PARK position.