Module, Body Control (BCM): Operation

A Body Control Module (BCM) is an electronic control unit with a micro controller that controls and integrates many of the main body electronic functions and features of the vehicle. Many of the functions and features provided by the BCM are possible because of numerous hard wired inputs and outputs, but most of these features are only possible or are enhanced because the BCM communicates electronically with other electronic modules in the vehicle as well as with a diagnostic scan tool using the Controller Area Network (CAN) data bus.

The BCM is a gateway between the high and low speed CAN data bus networks as well as a Local Interface Network (LIN) master node. This method of communication allows the sharing of sensor information, which reduces wire harness complexity, internal controller hardware and component sensor current loads. At the same time, this system provides increased reliability, enhanced diagnostics and allows the addition of many new feature capabilities. This method of communication is used by the BCM to acquire vehicle configuration data, including customer programmable features.

Software programming allows the BCM micro controller to monitor all of these inputs and provide the appropriate outputs through high side drivers, low side drivers, on-board relays, Pulse-Width Modulation (PWM) and electronic messages to other modules in the vehicle. Some of the functions and features that the BCM supports or controls include:

• Receives and transmits information on the B-CAN (e.g.: diagnosis, warning lights, controls, data)
• Receives and transmits information on the C-CAN
• Houses the gateway for communication between the B-CAN and C-CAN
• Is connected to the dashboard, front and cab wiring, managing numerous functions
• It allows interface for fault diagnosis
• Low consumption supply mode management (Logistic Mode)

• Entire system master: management of slave nodes in its direct jurisdiction and monitoring by other master nodes, monitoring and management of protocol errors, timer control
• Entire system fault diagnosis: collection of diagnostic information, management of fault diagnosis through WiTech
• Immobilizer: management of key code with possible engine ignition release
• Anti-theft: receiver management by remote control and connection with tilt sensors and alarm siren control unit
• Acquisition of on/off signals: reverse gear engaged, brake lights control, ignition switch position, door opening status switches, hazard warning lights control
• Acquisition of analogue signals: parking lights control, engine coolant level, brake fluid level, alternator voltage (D+), outside temperature signal, fuel level, battery voltage, windshield wiper intermittent device, main beam headlamps/flasher signal, direction indicators control, vehicle door locking/unlocking, windshield wiper selector signal, windshield washer selector signal, headlamp alignment adjustment signal, heated rear windshield control, rear fog lamps control, fog lights relay control
• Acquisition and repetition of vehicle speed signal
• Management of the courtesy lights with a timer and dimmer function
• Mnagement of ON/OFF outlets at relay: windshield washer pump, headlamp washer pump, fog lights, dipped headlamps, main beam headlamps, starting, windshield wiper (first and second speeds)
• ON/OFF management of one relay during left/right direction indicators or hazard warning lights for acoustic feedback
• ON/OFF output management directly at loads and light check function: front and rear side lights (left and right), front, rear and side direction indicators (left and right), number plate lights (left and right), brake lights (left and right), rear fog lamps (left and right)
• Bus line management for: rain/dusk sensor, alarm siren control unit, anti-tilt control unit