Circuit/System Verification
WARNING: This page is about a different car, the 2007 Chevrolet Monte Carlo and 2007 Chevrolet Impala. However, it is still accessible from the selected car via links, so may be relevant.
Ignition ON, cover the ambient light sensor, vary the interior lamp dimming switch from dim to full bright. The LED lamps in the HVAC control head, radio, DIC switch, and the steering wheel controls should dim and then become full bright.