Circuit/System Verification
WARNING: This page is about a different car, the 2009 GMC Sierra, 2009 Chevrolet Silverado, and 2009 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
Ignition ON, compare the scan tool BCM Prev. State of Charge and Start Up State of Charge parameters. The readings should not differ by more than 30 percent.