Brake Control Module (BCM)

Fig 1: Identifying Brake Control Module (BCM)

Courtesy of VOLVO CARS CORPORATION

The control module is installed with the ABS hydraulic modulator and is positioned on the cowl panel in the engine compartment. The electrical valve coils for the different hydraulic valves are integrated into the control module.

The main function of the control module is to process the signals from the different sensors and to control the hydraulic pump and the electromagnetic hydraulic valves (inlet and outlet valves) in the ABS hydraulic modulator during:

• ABS control
• EBD control
• Traction Control
• Active yaw control (DSTC).

The control module communicates with directly connected components and other control modules via the Controller Area Network (CAN).

Control modules with DSTC communicate with the steering wheel angle sensor which is integrated into the steering wheel module (SWM). The steering wheel angle sensor detects the movement of the steering wheel (steering angle).

The control module checks its calculations and all input and output signals using built-in diagnostic functions. When the vehicle is started and driven off, the control module checks that the signal from the wheel sensors is OK. When the car reaches 20 km/h (40 km/h if the stop (brake) lamp switch is activated), the control module briefly activates the pump motor and the hydraulic valves to check their function. The hydraulic pump can be heard at this time. This is completely normal. The ABS function can first be activated when the speed of the car exceeds approximately 7 km/h. Traction control however is available immediately. The control module also carries out a startup test and then activates the warning lights in the combined instrument panel which are connected to the functions in the system.

A diagnostic trouble code (DTC) is registered in the internal memory of the control module if it detects a fault. At the same time, a number of values are stored. These are frozen at the time the fault occurred. Depending on the severity of the fault, certain functions may be partially or completely disengaged. A warning lamp lights in the driver information module (DIM) to inform the driver that a fault has occurred. A warning or information text will also be shown in the display in the driver information module (DIM). The text displayed depends on the fault (see the table). Diagnostic trouble codes (DTCs) and frozen values (extended diagnostic trouble code (DTC) information) can be read off using VIDA (Volvo scan tool) via the data link connector (DLC) in the vehicle.