M57/M67 – Monitoring of the DDE control unit

The DDE control unit automatically performs several self-tests to ensure reliable operation.

In addition to the self-test at terminal 15 “ON” and constant background checks, safety-relevant functions are also
monitored. Monitoring includes:
• Main-relay activation
• Evaluation of the terminal 15 signal
• Monitoring of the microcontroller in coasting mode
• Test of the EAB function in operation
• Monitoring of the road-speed sensor
• Reactions to overspeed and system faults

Defect detection

A defect report causes the component in question to be provisionally tagged as defective. Defect classification is final
once a waiting period has elapsed without an intact message being sent in the meantime and a substitute function defined for this fault is activated.

Intact detection

Intact detection is analogous to defect detection. However, after the waiting time has elapsed, the fault is classified as “cured during operation” (= intact).

Fault code memory

A fault memory entry is generated as soon as the fault in question is tagged as confirmed. The fault entry in memory always includes the current mileage and the environmental conditions:

The fault memory is saved in the EEPROM of the control unit.
The corresponding indicator lights in the instrument cluster light up to notify the driver of engine-relevant faults. Exhaust-relevant faults are indicated only with catalytic converter monitoring.