Circuit/System Description: Notes
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.
Voltage is applied at all times to the low beam headlamp relay from battery voltage. Two different inputs to the body control module (BCM) can turn ON the low beam headlamps. The headlamp switch and the ambient light sensor.