Control module: Notes

The control module is integrated in the ESP unit and has a 31-pin connector. The control module also controls the joint functions of the ABS, EBD and TCS. Refer to "TECHNICAL DESCRIPTION " in WIS for further information.

The ESP function reduces engine torque and handle the braking on all four wheels. Torque reduction takes place after the ESP control module sends a bus message requesting a certain engine torque. The engine control module uses this request to regulate the air mass/combustion.

The ESP system utilizes the TCS function to a high degree, which means that ESP normally starts to function using Traction Control. If further action is required, it will be handled individually by braking the wheels until the car becomes stable again.

The stabilizing effect of the ESP system is based on calculations performed by the control module's microprocessor. The control module evaluates information from the system sensors: wheel speed sensors, steering wheel angle sensor, yaw rate sensor, lateral acceleration sensor and pressure sensor. Data from these sensors informs the control module of the driver's intentions, e.g. in which direction the driver wishes to drive, if the driver is braking, etc.

These values are processed by the control module. The control module also continually calculates the course of the car, the actual value, and compares this with desired direction indicated by the steering wheel, the desired value.

• If the car starts to under steer (when the front tends to continue straight ahead in a bend), the brakes will be applied on the inside rear wheel.
• If the car starts to over steer (the rear tends to drift out), the system will apply the brakes on the outside wheels until the measured and the calculated yaw rates correspond.

The control module contains a main relay and pump relay