Circuit Description
WARNING: This page is about a different car, the 2003 Pontiac Aztek and 2003 Buick Rendezvous. However, it is still accessible from the selected car via links, so may be relevant.
The BCM monitors the battery positive voltage and battery negative circuit voltage to determine if it is between 9.0-15.0 volts and sends this information out as a class 2 message to the VTD.