Circuit/System Description
WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2012 GMC Yukon XL, 2012 GMC Yukon, 2012 Chevrolet Tahoe, 2012 Chevrolet Suburban, and 2012 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.
When the headlamp and panel dimmer switch is placed in the AUTO position, the body control module (BCM) receives a ground signal through the headlamp switch headlamps OFF signal circuit. The headlamp and panel dimmer switch headlamps ON signal circuit and the park lamp switch signal circuit are both open and have no ground signal. When the headlamp and panel dimmer switch is placed in the PARK or HEAD position, the BCM will receive a ground signal through the headlamp switch headlamps ON signal circuit and the park lamp switch signal circuit. The headlamp switch headlamps OFF signal circuit will be open and have no ground signal.