Principles Of Operation

Body Control Module (BCM)

Principles of Operation

The Body Control Module (BCM) controls various systems by monitoring inputs from switches, sensors and messages sent over the Medium Speed Controller Area Network (MS-CAN) from other modules. The BCM activates outputs based on the inputs received. For example, the BCM monitors the headlamp switch position, and based on this input, the BCM may provide voltage to the exterior lamps.

Field-Effect Transistor (FET) Protection

A Field-Effect Transistor (FET) is a type of transistor that, when used with module software, monitors and controls current flow on module outputs. The FET protection strategy prevents module damage in the event of excessive current flow.

The BCM utilizes a FET protective circuit strategy for many of its outputs (such as a turn lamp output circuit). Output loads (current level) are monitored for excessive current (typically short circuits) and are shut down when a fault event is detected. A short circuit DTC sets when the fault event occurs.

The circuit remains off until the fault is corrected and the ignition state is cycled off and then back on, the module resets the FET protection and allows the circuit to function.