Circuit/System Verification
WARNING: This page is about a different car, the 2007 Pontiac Torrent and 2007 Chevrolet Equinox. However, it is still accessible from the selected car via links, so may be relevant.
Ignition ON, turn the park lamps ON, observe the back lighting in the instrument panel (I/P). The back lighting should turn ON and the intensity will change with the operation of the dimmer switch.