For 1990-2009 cars

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

• | The body control module (BCM)

• | The DRL relay

• | The headlamps

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 placing both headlamps in series with each other. 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 (A-Oldsmobile) of the left headlamp instead of battery positive voltage through CKT 150 and CKT 593 (refer to Headlights Circuit Description for a description of normal headlights operation. Battery positive voltage for the DRLs is supplied through the RH HDLP fuse (CKT 640) to terminal B (A-Oldsmobile) of the right headlamp. With ground at terminal B (A-Oldsmobile) of the left headlamp and battery positive voltage at terminal B (A-Oldsmobile) of the right headlamp, both headlamps will illuminate at a reduced intensity compared to normal headlamp operation.