Circuit/System Description
WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2012 GMC Yukon XL, 2012 GMC Yukon, 2012 Chevrolet Tahoe, 2012 Chevrolet Suburban, and 2012 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.
The body control module (BCM) monitors the state of charge of the electrical system. If the BCM senses that the state of charge at ignition On is 30 percent lower than what it was when the engine was running.