Daytime Running Lamp: Description and Operation

DAYTIME RUNNING LAMPS (DRL)

The daytime running lamps (DRL) will illuminate the right and left front turn signal bulbs continuously. The DRLs will operate when the following conditions are met:
1. The ignition is in the RUN or CRANK position
2. The shift lever is out of the PARK position for vehicles equipped with automatic transmissions or the parking brake is released for vehicles with manual transmissions.
3. The high and low beam headlamps are OFF.

The ambient light sensor is a light sensitive transistor that varies the voltage signal to the body control module (BCM). The BCM sends a signal via GMLAN serial data commanding the front turn lamps on steady (non-flashing). Any function or condition that turns on the headlamps will cancel the DRL operation. With the turn signal/multifunction 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.