Body Control Module (BCM) - System Operation and Component Description: Notes

WARNING: This page is about a different car, the 2019 Ford F-550 Super Duty, 2019 Ford F-450 Super Duty, 2019 Ford F-350 Super Duty, and 2019 Ford F-250 Super Duty. However, it is still accessible from the selected car via links, so may be relevant.

System Operation

Body Control Module (BCM)

The BCM controls various systems by monitoring inputs from switches, sensors and network messages from other modules on the HS-CAN1 and from the GWM. Based on the inputs received, the BCM activates outputs. For example, the BCM monitors the headlamp switch position. Based on this input, the BCM may provide voltage to the exterior lamps.

Battery Saver

The battery saver feature is used to conserve battery voltage. The BCM provides automatic shut-off of the interior lamps after a time-out period when the ignition is off.

Refer to: INTERIOR LIGHTING

Battery Load Shed

The BCM monitors the battery state of charge and when necessary will shut off accessories in order to save the remaining battery charge. Refer to: Charging System - System Operation and Component Description .

Field Effect Transistor (FET) Protection

The BCM utilizes an Field Effect Transistor (FET) protective circuit strategy for many of its outputs, for example, lamp output circuits. Output loads (current level) are monitored for excessive current (typically short circuits) and are shut down (turns off the voltage or ground provided by the module) when a fault event is detected.

A Field Effect Transistor (FET) is a type of transistor that the control module software uses to control and monitor current flow on module outputs. The Field Effect Transistor (FET) protection strategy prevents module damage in the event of excessive current flow.

Output loads (current level) are monitored for excessive current draw (typically short circuits). When a fault event is detected the Field Effect Transistor (FET) turns off and a short circuit DTC sets. The module resets the Field Effect Transistor (FET) protection and allows the circuit to function when the fault is corrected or the ignition state is cycled off and then back on.

When the excessive circuit load occurs often enough, the module shuts down the output until a repair procedure is carried out. Each Field Effect Transistor (FET) protected circuit has 3 predefined levels of short circuit tolerance based on a module lifetime level of fault events based upon the durability of the Field Effect Transistor (FET). If the total tolerance level is determined to be 600 fault events, the 3 predefined levels would be 200, 400 and 600 fault events.

When each level is reached, the DTC associated with the short circuit sets along with DTC U1000:00. These Diagnostic Trouble Codes (DTCs) can be cleared using the module on-demand self-test, then the Clear DTC operation on the scan tool (if the on-demand test shows the fault corrected). The module never resets the fault event counter to zero and continues to advance the fault event counter as short circuit fault events occur.

If the number of short circuit fault events reach the third level, then Diagnostic Trouble Codes (DTCs) U1000:00 and U3000:49 set along with the associated short circuit DTC. DTC U3000:49 cannot be cleared and the module must be replaced after the repair.

Post Crash Alert Function

The post crash alert is a function controlled by the BCM. If the RCM determines an impact of enough severity has occurred (the airbags may or may not be deployed), the post crash alert function activates.

The post crash alert function:

sounds the horn.
turns on the hazard lights.
turns on the interior lights.
unlocks the doors.

The post crash alert function can be turned off by:

pressing the hazard flasher lamp switch (which may need to be pressed twice).
pressing the transmitter unlock button.
cycling the ignition switch (RUN-OFF-RUN-OFF-RUN).
opening the driver door.

Factory-Transport Mode

During vehicle build, some modules (such as the IPC and the BCM) are set to factory mode. When the vehicle build is complete, the vehicle is set to transport mode. If the IPC displays FACTORY MODE in the message center, Refer to: Factory Mode Deactivation .

Transport mode is used to reduce the drain on the battery during longer periods when the vehicle is not used. Various system functions can be altered or disabled when in the transport mode. While in transport mode, the IPC displays TRANSPORT MODE in the message center. Transport mode can be disabled and placed into normal operation mode. Refer to: Transport Mode Deactivation .

Car Configuration Parameters

The parameters are set in the BCM. The parameters are also set in the IPC as backup data for service, in case online As-Built data is not available. For more information, Refer to: Module Programming .

Power Points

This vehicle is equipped with front instrument panel and seat 12 volt power outlets and center console (if equipped).

The power point relays are located in the BJB and are non-serviceble. The relays are Hot at all times. Circuits are protected by quick blow fuses located in the BJB. For additional information, refer to Owner Information.