Principles of Operation: Notes
WARNING: This page is about a different car, the 2014 Ford F-150. However, it is still accessible from the selected car via links, so may be relevant.
The Body Control Module (BCM) controls various systems by monitoring inputs from switches, sensors and messages sent from other modules. The BCM activates outputs based on the inputs received. For example, the Steering Column Control Module (SCCM) monitors the headlamp switch and transmits the headlamp switch position to the BCM over the network. Based on this input, the BCM may provide voltage to the exterior lamps.