Control Module

The control module is integrated in the ABS hydraulic modulator and is located in the engine compartment. The control module contains the electrical valve coils for the different hydraulic valves.

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 when controlling the:

• ABS
• EBD
• TRACS
• STC or
• DSTC.

Control modules with the DSTC (dynamic stability and traction control) function also have external sensors which sense the driver's steering wheel movements and the directional behavior of the car.

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

The control module checks calculations and all input and output signals via the built-in diagnostic functions. When the control module detects a fault certain functions are completely disengaged depending on the severity of the fault. At the same time a warning light comes on depending on the fault. During manual disengagement of TRACS/STC/DSTC the control module stops all the functions except for the ABS, Electronic brake force distribution and vehicle speed signal. If the temperature of the brake discs is too high, certain functions are prevented from operating.

Any diagnostic trouble codes (DTC) are stored in the control module memory. This information can be read off using VIDA via the data link connector (DLC) in the car.

When the car is driven the control module checks that a signal is received from the wheel sensors. When the car reaches 20 km/h for the first time (40 km/h if the stop (brake) lamp switch is activated) the control module checks the pump motor and the hydraulic valves by quickly activating them. A noise is then heard from the hydraulic pump, this is completely normal. The ABS function first becomes available when the vehicle speed exceeds approximately 7 km/h. The ABS function is active until the vehicle speed falls below approximately 4 km/h, when the function is disengaged. Traction control is available from standstill.