Voltage supply and main relay DDE 5.1

The DDE control units are supplied with power via the 58-pin control unit connector.

Function

The power supply to the DDE control units follows the following sequence when the ignition is switched on:

• With ignition ON, the CAS switches voltage to the DDE master control unit via terminal 15WUP. This signal is forwarded to the DDE slave control unit via terminal S_KL15.
  
• The DDE master control unit switches on the DDE main relay 1 and DDE main relay 2 via S_HR
  
• The both DDE main relays switch terminal 30 via U_HR to the DDE control units
  

Troubleshooting

The following faults are monitored in the voltage supply system:

• Fault 4660/4661: Voltage of power supply to DDE control unit too high/low
  
• Fault 4120/4121: DDE main relay switches off too soon/too late