Circuit/System Verification
WARNING: This page is about a different car, the 2016 GMC Acadia, 2016 Chevrolet Traverse, and 2016 Buick Enclave. However, it is still accessible from the selected car via links, so may be relevant.
Ignition ON, command the Left Rear Window Up and Down and the Right Rear Window Up and Down with a scan tool. The left rear window and the right rear window should perform the UP and DOWN function.