Daytime Running Lamps

WARNING: This page is about a different car, the 2005 Saturn L300. However, it is still accessible from the selected car via links, so may be relevant.

Daytime running lamps (DRL) are controlled by the BCM based on input from the high beam headlamp circuit 1200, the low beam headlamp circuit 1201, the parking brake circuit 1134 and ignition switch state.

When DRL operation is desired, the body control module (BCM) switches circuit 592 to ground. This action energizes the DRL relay. When energized, the DRL relay operates high beam headlamps or low beam headlamps (later models) as a series circuit, one-half of battery voltage across each high beam headlamp.

When DRL operation is not desired, the BCM does not provide ground for the DRL relay. When not energized, as when high beam headlamps or low beam headlamps (later models) are desired, the DRL relay operates the high beam headlamps or low beam headlamps (later models) as a parallel circuit, full battery voltage across each headlamp.

For DRL operation, the parking brake must be fully released, the ignition switch must be in the RUN position and headlamp switch must be in the Off position. Under normal operating conditions, the feedback voltage to the BCM measured at circuit 1200 is (see table below):

Body Control System Description and Operation

Headlamp	Circuit 1200 or Circuit 1201 (later models) Voltage
DRL ON	6 to 8 Volts
High beam or low beam (later models) ON	Less than 1 Volt
High beam or low beam (later models) OFF	Battery Voltage