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
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 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.