Circuit/System Description
WARNING: This page is about a different car, the 2010 Cadillac SRX. However, it is still accessible from the selected car via links, so may be relevant.
The headlamp switch is supplied with ground at all times. When the headlamp switch is placed in either the park or low beam position, the BCM responds by applying battery voltage to the license plate lamp control circuit. This energizes the left and right license lamp.