Normal Operation
WARNING: This page is about a different car, the 2006 Mercury Grand Marquis and 2006 Ford Crown Victoria. However, it is still accessible from the selected car via links, so may be relevant.
The lighting control module (LCM) sends voltage signals to the headlamp switch through circuits 220 (VT/OG), 1400 (TN/WH), 1032 (WH/BK) and 1033 (RD/YE). The headlamp switch routes a signal to ground through circuit 57 (BK) for any given headlamp switch position. If the LCM detects a fault with the headlamp switch input, the LCM defaults the exterior lamps on.
When a request for the autolamps is detected, the LCM sends a voltage reference signal to the light sensor through circuit 218 (WH/VT). The light sensor is provided ground through circuit 676 (PK/OG). When the light sensor does not pull the voltage signal low (low ambient light condition), the LCM provides voltage to the exterior lamps.