Diagnostic Aids
WARNING: This page is about a different car, the 2013 GMC Yukon XL, 2013 GMC Yukon, 2013 Chevrolet Tahoe, 2013 Chevrolet Suburban, and 2013 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.
If the 5-volt reference or the switch signal wire are shorted to ground the scan tool can show up to 7.5 volts.