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The vehicle control unit (DDEC-VCU) communicates between the DDEC-ECU and other electronic control units installed on the vehicle over the J1587 datalink. See Figure 43384 . Within the DDEC-VCU, sets of data for specific applications are stored. These include idle speed, maximum running speed, and speed limitation. ‪

Vehicle Control Unit (DDEC-VCU)

The DDEC-VCU receives data from the following sources: ‪

  • The operator (accelerator pedal position, engine brake switch)
  • Other electronic control units (for example, the anti-lock brake system)
  • The DDEC-ECU control unit (data such as oil pressure and coolant temperature)

From this data, instructions are computed for controlling the engine and transmitted to the DDEC-ECU via the proprietary datalink. The DDEC-VCU controls various systems, for example, communications with the datalink, the engine brake, and the constant-throttle valves. If the engine control system detects a fault, the appropriate fault code is broadcast on the datalink and can be read using minidiag2. When there is a fault, the code for the control unit reporting the fault can be read directly on the ICU display. ‪