Daytime Running Lamp: Description and Operation

DAYTIME RUNNING LAMPS (DRL)

The low beam headlamps operate at reduced intensity when in daytime running lamps (DRL) mode. The ground circuit to the switch side of the DRL relay has a resistor in-line to reduce the intensity of the low beam headlamps for DRL operation. The body control module (BCM) receives a signal from the ambient light sensor indicating a low or high ambient, outside, light level. Under daylight conditions the BCM grounds the DRL relay control circuit energizing the DRL control relay. The now closed relay supplies ground directly to the low beam headlamps and to the BCM on the headlamp low beam signal circuit. The low beam headlamps now illuminate with reduced intensity. The DRL relay is grounded at G203. Any time the headlamps are illuminated the DRL will not illuminate. Manual park lamps do not effect DRL operation.

The conditions necessary for the BCM to illuminate the DRL are as follows:
- The ignition switch is in the RUN position.
- The headlamps are in the OFF position.
- The park brake is OFF, released.
- The BCM is receiving a high light condition from the ambient light sensor.
- The transmission is not in the PARK position.