Headlamp: Description and Operation

HEADLAMP POWER
The headlamp switch is a direct input to the BCM. The BCM sends a BUS message to the Front Control Module (FCM) informing it of a headlamp switch status change. The FCM then turns on power to the headlamps through four "fuseless" circuits. These circuits are electronically controlled and continuously monitored for malfunctions. Power is supplied to each filament in a separate circuit. For vehicles equipped with Daytime Running Lamps (DRL), the FCM electronically steps down the headlamp voltage to provide the desired illumination.

AUTO HEADLAMPS
This feature is available on vehicles equipped with both the Electrochromatic Mirror (ECM) and the Compass/Mini-Trip Computer (CMTC). When the BCM detects a day/night signal from the CMTC, an ECM is present and Auto Headlamp mode is selected.