DTC 21

DTC 21

21 Supply voltage terminal 87 (overvoltage/undervoltage)
Over-and undervoltage are detected by monitoring the battery voltage at terminal 29 of the Tiptronic control module. The fault is reset if the Tiptronic voltage supply is located within the limits 9 V < U(Batt) < 16.4 V

NOTE: The redundancy transistor is switched off. The setpoint values of the current regulator are set to 0 and all change-over valves are switched off. The control module is then in emergency operation.

Diagnosis conditions
- Ignition on
- Tiptronic voltage supply to pin 29 less then 8.5 V or greater then 16.9 V

Possible fault cause
- Voltage too high or low
- Fault in alternator
- Connection to Tiptronic control module is faulty

Affected terminals
Terminal 29

Diagnosis/Troubleshooting