The ABS safety lamp and the ASC multifunction lamp light for approx. 2 seconds (lamp check) as from ignition lock position 2 and then go out if no faults are found in the ABS/ASC system.
If the ABS safety circuit detects a fault in the ABS subsystem, the ABS and ASC systems are deactivated and the ABS safety lamp as well as the ASC multifunction lamp light up.
If the fault no longer applies during the next start procedure, the lamps will go out after the lamp check.
If the ASC safety circuit detects a fault in the subsystem ASC, depending on the type of fault, either both subsystems or only the ASC subsystem are deactivated and the corresponding lamps light up.
If the ASC system is switched on manually in passive mode, this situation is indicated to the driver by the steady light of the ASC multifunction lamp.
The driver's attention is drawn to an ASC control function by the ASC multifunction lamp flashing (3 Hz).
Note
The ABS safety lamp and the multifunction lamp light permanently during diagnosis (communication with the tester).
The DME main relay provides the positive supply of the control unit as of ignition lock position 2. The voltage is retained for approx. 5 seconds after "ignition OFF". (DME holding circuit)
Ground connection is realized via three ground lines.
The ABS/ASC control unit acquires the wheel speed signals via the speed sensors, processes the signals and then makes them available for other users such as the EGS, IKE (speedometer signal) or the EDC.
The ABS/ASC control unit outputs the speed output signals as square-wave signals with constant amplitude (low level <1 V / high level > 11 V). The frequency of the square-wave signal is dependent on the relevant wheel speed in the range from 0 to 1700 Hz (0 to 250 km/h).
The brake light switch signal serves as a redundant signal for recognizing an initiated braking procedure. This enables improvements in control comfort.
Faults in the brake light switch circuit are stored in the fault code memory, however, the ABS safety lamp is not activated when such faults occur.
The handbrake switch signals informs the ABS/ASC control unit that it is possible that the car is being driven with the handbrake applied.
This causes the control unit to set a higher threshold value for the engine drag torque control (idle speed increase).
The ASC system can be switched off and on while driving with the aid of the ASC button. The ASC safety circuit is always active. The ASC system is active after every new start (as from ignition lock position 2).
The terminal 61 signal is a redundant signal and serves the purpose of detecting whether the engine is running. At an alternator voltage below 8 V, the ASC system switches off and the multifunction lamp lights up. However, no fault is stored in the defect code memory.