Circuit/System Verification
WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2007 GMC Yukon XL, 2007 GMC Yukon, 2007 Chevrolet Tahoe, 2007 Chevrolet Suburban, and 2007 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.
Ignition ON, headlamp switch to PARK, just the park lamps should illuminate. Headlamp switch to HEAD, the park lamps and headlamps should illuminate.