Circuit/System Description
WARNING: This page is about a different car, the 2016 GMC Acadia, 2016 Chevrolet Traverse, and 2016 Buick Enclave. However, it is still accessible from the selected car via links, so may be relevant.
When the headlamp switch is in the OFF position, the body control module (BCM) receives a ground signal through the headlamp switch OFF circuit and an open signal on the park lamp ON circuit and headlamps ON circuit. When the headlamp switch is in the PARK or HEAD position, the BCM receives an open signal through the headlamp switch OFF circuit and a ground signal through the park lamp ON circuit or headlamp ON circuit.