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.
Ignition ON, transmission in REVERSE, verify that the scan tool Sensor Supply Voltage parameter is between 7.2-9.2 V.