9. Diagnosis & failsafe

W HEEL SENSOR CHECK FLOW

MOTOR/SOLENOID CHECK

SAFETY CONCEPT OF THE ESP CONTROL UNIT

In an emergency, it is vital that all ESP components function with absolute reliability. For this reason, various safety options must be available which guarantee the function of the system. The most important of these safety options are:

• self-test of the electronic control unit

• peripheral test of the connected assemblies

SAFETY AND MONITORING SYSTEM

Turning on the ignition activates a self-test of the electronic control unit. After staring, all electric connections are monitored continuously.

During the trip, the solenoid valves are checked at regular intervals by means of passive test pulses. In addition, all sensor signals are monitored continuously. The separation of brake circuits enables the ABS function to be maintained if one brake circuit should fail. This means that the driving stability of the vehicle is maintained during critical braking maneuvers.

For workshop diagnosis, all faults detected are stored in a nonvolatile memory in the ESP control unit for retrieval in the workshop location.

System monitoring

The following items are controlled by the ECU:

• 12 valves • ABS pump • ABS/ESP warning lamps

The following items are monitored by the ECU:

• Electronic control unit (include pump and valves) • Wheel speed sensors • Yaw rate sensor • Lateral acceleration sensor • G sensor (for ABS of 4WD vehicle) • Pressure sensor • Onboard voltage • CAN bus communication

The warning lamps, the brake light switch and the ESP on/off switch are not monitored.