Daytime Running Lamp: Description and Operation

DAYTIME RUNNING LAMPS (DRL)

The ambient light sensor is a light sensitive transistor that varies the voltage signal to the HVAC control assembly. The HVAC control assembly then sends a signal to the BCM through the class 2 message circuit commanding the BCM to turn the front turn lamps on steady (non-flashing). Any function or condition that turns on the headlamps will cancel the DRL operation. With the headlamp switch in the OFF position, the turn signal lamps will either be turned ON or OFF after a 30-second delay, depending on whether daylight or low light conditions are sensed by the ambient light sensor. The DRL operates when the ignition switch is in the RUN position, the parking brake is not set and the transmission is not in the PARK position. When these conditions have been met, and the ambient light sensor indicates daytime conditions the DRL lamps will illuminate.