Body Control Module (BCM): Notes

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

System Operation

BCM 

The BCM controls various systems by monitoring inputs from switches, sensors and network messages from other modules and components on the HS-CAN, MS-CAN, LIN and the GWM. Based on these inputs, the BCM activates many outputs. For example, the BCM monitors the HCM inputs and provides voltage to the exterior lamps. Or the DCMH to provide power and ground for the sliding door latch.

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. For additional information, Refer to: Interior Lighting - System Operation and Component Description .

Body Control Module C 

The BCMC controls various systems by monitoring inputs from switches, sensors and network messages from other modules and components on the HS-CAN1. Based on these inputs, the BCMC activates outputs. For example, the BCMC provides power to the high voltage battery coolant diverter valve, motor electronics coolant pump, the high voltage battery coolant pump and park by wire motor and solenoid. Furthermore, the BCMC also provides 12V power to the high voltage battery contactor control relays when the ignition is turned ON.

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 (turns off the voltage or ground provided by the module) 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 is cycled off and then back on. The module then resets the FET protection and allows the circuit to function. After a preset number of retries with the short circuit present the output is shut down for all drive cycles until the fault is repaired, the related DTC is cleared and the BCM passes a self-test.

A module lifetime is established based upon the durability of the FET. If an output has reached the maximum number of activations the BCM sets DTC U3000:49. When DTC U3000:49 sets and the Diagnostic Trouble Codes (DTCs) are cleared the short circuit DTCs no longer sets to indicate the type of fault on the output circuit before permanent deactivation occurred. Once the number of short circuit fault events reach a predetermined maximum level, DTC U3000:49 cannot be cleared and the module must be replaced after the initial fault is repaired to return the associated functionality to the vehicle.

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.

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.

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 (not applicable to vehicles equipped with low level message center display). Transport mode can be disabled and placed into normal operation mode. For additional information, Refer to: Factory Mode Deactivation . .

Module Configuration Parameters 

The parameters are set in the BCM. For additional information, Refer to: the appropriate Module Communications Network service information.

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. When the relays set, the power points are hot at all times. Circuits are protected by quick blow fuses located in the BJB. For additional information, refer to Owner Information.