Control Module

Courtesy of VOLVO CARS CORPORATION

The control module is mounted with the hydraulic unit as a unit and is located on the cowl panel in the engine compartment. The electrical valve coils for the different hydraulic valves are integrated into the control module.

The most important function of the control module is to process the signals from the various system sensors as well as those from other control modules an to use the signals to regulate the hydraulic pump and the electromagnetic hydraulic valves (intake and outlet valves) in the hydraulic unit during:

• ABS control
• EBD control
• AYC control
• EBA control

The control module communicates with directly connected components and other control modules via CAN.

To ensure that the hydraulic pump works, a self test is performed, where the brake control module (BCM) briefly activates the hydraulic pump and measures the current as it rotates. This occurs as the brake pedal is released. In vehicles with an automatic gearbox, this is experienced as when the vehicle starts to roll. The hydraulic pump and valves can be heard, which is normal.

The ABS function can be activated once vehicle speed exceeds approx. 7 km/h (4.3 mph). The traction control function, however, is operable right from the start. The control module also performs a start-up test, at which time the warning lamps that are linked to the functions in the system are activated in the driver information module.

If the control module detects a fault, it stores a diagnostic trouble code in its internal memory. A number of values that were frozen at the time the fault occurred are stored at the same time. 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 is determined by the type of fault (see the table). Diagnostic trouble codes and frozen values can be read off using the diagnostic tool via the data link connector in the vehicle.