Module Controlled Functions: Notes

Module Controlled Functions - 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 on the FD-CAN1. 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.

BCMC 

The BCMC may be referred to as a BJB or a Power Distribution Box (PDB). The BCMC controls various systems by monitoring inputs from switches, sensors and network messages from other modules and components on the HS-CAN. Based on these inputs, the BCMC activates outputs. For example, the BCMC controls the A/C clutch control relays and VDM circuit outputs.

UCIM 

The UCIM is an optional factory-installed device that easily allows a direct CAN programmable logic interface to control devices such as salt spreaders or lifts quickly and simply by using a laptop or notebook.

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. The battery current sensor which monitors current flow in and out of the battery is attached to the battery negative cable. It is supplied a 5-volt reference voltage and a ground from the BCM.

FET Protection 

The BCM utilizes a 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 FET is a type of transistor that the control module software uses to control and monitor current flow on module outputs. The FET protection strategy prevents module damage in the event of excessive current flow.

When a fault event is detected the FET turns off and a short circuit DTC sets. The module resets the 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 FET protected circuit has three predefined levels of short circuit tolerance based on a module lifetime level of fault events based upon the durability of the FET. For example, if the total tolerance level is determined to be 600 fault events, the three 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) are cleared by 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, 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 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 are altered or disabled when in the transport mode. While in transport mode, the IPC displays TRANSPORT MODE  in the message center. Transport mode is 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 additional information, Refer to: Module Configuration - System Operation and Component Description .. Or, Refer to: Module Configuration - Electric - System Operation and Component Description .