Circuit/System Description
WARNING: This page is about a different car, the 2010 Chevrolet Camaro. However, it is still accessible from the selected car via links, so may be relevant.
When the headlamp switch is placed in the headlamp position, ground is applied to the body control module (BCM) through the headlamp low beam signal circuit. The BCM responds to this input by applying ground to the headlamp low beam relay control circuit which energizes the low beam relay. With the low beam relay energized, the switch contacts close allowing battery voltage to flow through the left and right HID fuses to the low beam headlamps.