Automatic Headlamps Operation
WARNING: This page is about a different car, the 2006 Buick Lucerne. However, it is still accessible from the selected car via links, so may be relevant.
When the ambient light sensor detects a low light condition, the BCM then applies a ground to the headlamp low beam relay control circuit. This energizes the LO BEAM PCB Relay and voltage is applied through the switch side of the relay and both low beam headlamp fuses to the low beam headlamps.