Daytime Running Lamps (DRL)

WARNING: This page is about a different car, the 2007 Cadillac DTS. However, it is still accessible from the selected car via links, so may be relevant.

The front turn signal lamps are used for DRL operation. The DRLs will operate only when the engine is running and the headlamp switch is in the AUTO position. When the DRLs are ON, no other exterior lamps such as the parking lamps, tail lamps, etc. will be ON. Also, the instrument panel will not be illuminated.

DRL operation is determined by the ambient light sensor and the controlled by the body control module (BCM). The ambient light sensor is a light-sensitive transistor used to monitor outside lighting conditions. The BCM provides a 5-volt reference signal to the sensor while ground is provided at G300. The sensor will vary this voltage signal between 0.2 and 4.9 volts depending on outside lighting conditions. The BCM monitors the ambient light sensor signal circuit to determine if outside lighting conditions are correct for either DRL or headlamp operation. When the BCM determines the conditions are met for DRL operation, it turns ON the front turn signal lamps in a steady non-flashing mode. Any function or condition that turns on the headlamps will cancel DRL operation.

When the BCM detects low light conditions, it will turn OFF the daytime running lamps and turn ON the low beam headlamps as described above in Low Beam Headlamp Operation. The BCM will also turn ON the low beam headlamps in daylight conditions when the windshield wipers are turned ON.