Power Mode
WARNING: This page is about a different car, the 2003 Saturn LW300, 2003 Saturn LW200, 2003 Saturn L300, and 2003 Saturn L200. However, it is still accessible from the selected car via links, so may be relevant.
The BCM monitors ignition 1 voltage circuit 339, accessory 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.