Circuit Description
WARNING: This page is about a different car, the 2004 Buick Regal and 2004 Buick Century. However, it is still accessible from the selected car via links, so may be relevant.
The body control module (BCM) monitors the Ignition 0, Ignition 1, Crank and Accessory circuits from the ignition switch. The BCM uses the voltage state (B+ or 0) and the sequence of state changes to determine the power mode called for by the ignition switch. Refer to the table in Body Control System Description and Operation .