GM Service Manual Online
For 1990-2009 cars only

The daytime running lights (DRL) system is comprised of the following components:

    • The body control module (BCM)
    • The DRL relay
    • The headlamps
    • The DRL resistor

The following conditions must be present to allow the DRLs to illuminate:

    • The ignition must be on.
    • The park brake must be unapplied.
    • The transaxle must be in any position except PARK.

When the above conditions are met, the BCM will supply ground to the DRL relay engaging the relay. Battery voltage for the DRL relay is supplied through the HTR-A/C IGN fuse. When the DRL relay is energized, ground is supplied to terminal B of the low beam headlamps via circuits 589 and 1201 through the DRL resistor.