Circuit/System Description
WARNING: This page is about a different car, the 2008 GMC Sierra, 2008 GMC Cab & Chassis Sierra, 2008 Chevrolet Silverado, and 2008 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
When the headlamp switch is in the AUTO position, the body control module (BCM) receives a ground signal through the headlamp switch headlamps OFF signal circuit and no signal on the headlamp switch headlamp ON signal circuit and headlamp switch park lamps ON signal circuit. When the headlamp switch is in the PARK or HEAD position, the BCM receives no signal through the headlamp switch headlamps OFF signal circuit and a ground signal through the headlamp switch headlamp ON signal circuit and headlamp switch park lamps ON signal circuit.