Circuit/System Verification
WARNING: This page is about a different car, the 2010 Saturn Outlook, 2010 GMC Acadia, 2010 Chevrolet Traverse, and 2010 Buick Enclave. However, it is still accessible from the selected car via links, so may be relevant.
Command the Rear Defog Request ON and OFF with the scan tool. The rear window defogger should turn ON and OFF when changing between the commanded states.