Circuit/System Verification
WARNING: This page is about a different car, the 2008 Buick LaCrosse and 2008 Buick Allure. However, it is still accessible from the selected car via links, so may be relevant.
Start the engine in PARK and observe the Ignition Voltage parameter on the scan tool. The Ignition Voltage should be between 12.0-14.5 volts.