Power Mode
WARNING: This page is about a different car, the 2003 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.
The BCM monitors ignition 1 voltage circuit 339, ACC voltage circuit 743 and the engine run flag (ERF). The ERF is a serial data message from the engine controller. The BCM determines the state of the ignition switch for all modules on the serial data link.