Engine Control Module: Description and Operation

Voltage Supply And DDE Main Relay

The voltage supply of the DDE control unit is realized via the 58-pin control unit connector.

Function
The voltage supply of the DDE control unit is effected in the following steps when the ignition is switched on:
- At ignition ON there is voltage at the DDE control unit via terminal 15 or the wake-up line
- The DDE control unit switches the DDE main relay on via S_HR
- The DDE main relay switches terminal 30 via U_HR to the DDE control unit

Fault handling
The voltage supply is monitored for the following faults:
- Fault 4660/4661: supply voltage at DDE control unit exceeded /undershot
- Fault 4120/4121: DDE main relay switches off too late/too soon