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MBE 900 DDEC-ECU (ENGINE CONTROL UNIT)

The DDEC-ECU or engine-resident control unit is located on the left-hand side of the engine. See Figure 42949 . The DDEC-ECU is connected by a proprietary datalink to the vehicle control unit (DDEC-VCU). All necessary data and information is exchanged through the datalink. The DDEC-VCU then broadcasts all information on the J1587 and J1939 data links, where it can be read by minidiag2. ‪

The DDEC-ECU processes the data received from the DDEC-VCU, for example the position of the accelerator pedal, engine brake, etc. ‪

These data are evaluated together with the data from the sensors on the engine, such as: ‪

  • Intake manifold pressure and temperature
  • Coolant temperature
  • Fuel temperature
  • Oil pressure

The data is then compared to the characteristic maps or lines stored in the DDEC-ECU. ‪

From these data, quantity and timing of injection are calculated and the unit pumps are actuated accordingly through the solenoid valves. ‪

DDEC-ECU Control Unit Location

Note: To obtain a replacement DDEC-ECU control unit, all the data given on the DDEC-ECUcontrol unit data plate is required. The data plate is located on the face of the DDEC-ECU unit. See Figure 42591 .

Control Unit Data Plate

DDEC-ECU Control Unit Removal

Remove the DDEC-ECU as follows: ‪

  1. Open the hood.
  2. Disconnect the oil level sensor wiring from the DDEC-ECU control unit by removing the bolt holding it in place.
  3. Pull up on the locking bar on the vehicle wiring harness connector and disconnect it from the DDEC-ECU unit. See Figure 42421 .

    1. Engine Trim Panel ‪

    5. Locking Bar ‪

    2. Spacer ‪

    6. Vehicle Wiring Harness ‪

    3. Rubber Damper ‪

    7. Engine Wiring Harness ‪

    4. Hex bolt ‪

    DDEC-ECU Control Unit Removal

  4. Rotate the locking bar on the engine wiring harness connector and disconnect it from the DDEC-ECU unit.
  5. Remove the four hex bolts and rubber dampers holding the DDEC-ECU control unit to the engine. Then remove the unit.

    Note: Do not disassemble the DDEC-ECU control unit. It cannot be serviced.

DDEC-ECU Installation

Install the DDEC-ECU as follows: ‪

  1. Using the four spacers and hex bolts, and eight rubber dampers, attach the DDEC-ECU control unit to the engine. Make sure the rubber dampers are installed correctly, with the flanged ends outboard. See Figure 42421 .

    1. Engine Trim Panel ‪

    4. Hex bolt ‪

    2. Spacer ‪

    5. Vehicle Wiring Harness ‪

    3. Rubber Damper ‪

    6. Engine Wiring Harness ‪

    DDEC-ECU Control Unit Installation

  2. Tighten the hex bolts 15 Nm (11 lbft).
  3. Connect the engine wiring harness and the vehicle wiring harness to the DDEC-ECU. Lock them in place.
  4. If a new DDEC-ECU control unit was installed, transfer the new dataset to it, using the applicable diagnostic tool.
  5. Close the hood. Then check for normal operation.