Engine Tier-3 710655- Ch 1 page 27 Engine control unit, ECU This engine has an electronic management system, ECU Engine Control Unit (also called EMS, Electronic Management System) with unit injectors (PDE) which provide each cylinder with the right amount of fuel at the right time in all operating situations. The ECU system consists of a control unit (S6) and sensors for speed, charge air temperature and pressure, coolant temperature, oil pressure, accelerator pedal/throttle actuation which constantly emit signals to the con trol unit.
With the aid of this input data and the programmed control software, the correct fuel amount and correct injec tion time are calculated for each unit injector (PDE) under the specific operating conditions. The ECU system sensors can also be used to emit signals to the instruments in the instrument panel. The control unit constantly checks the sensors to make sure they are operational. The control unit contains monitoring functions to protect the engine in the event of a fault which would otherwise damage it. In the event of a fault, e.g. alarm level for low oil pressure or high coolant temperature, the S6 control unit sends a CAN message to a coordinator.
The main task of the coordinator is to pass on data by means of CAN communication from the engine control unit to other control units and signals to gauges and lamps in the instrument panel. The coordinator also has monitoring functions. When the ECU control unit detects a fault, the control unit diagnostics lamp comes on (left-hand lamp on the instrument panel) and it stays on as long as the fault is active. At the same time, a fault code is generated which can be read off via the coordinator on the diagnostics lamp in the form of a flashing code when a separate diag nostic switch is actuated. A flashing code may consist of a number of different fault codes.
When the coordinator detects a fault, a fault code is generated which can be read off on the coordinator di agnostics lamp (the left-hand lamp on the instrument panel) in the form of a flashing code when a separate diagnostic switch is actuated. If the torque reducing function is activated, the fuel amount is reduced to 70%, and if the engine shutoff function is actuated, the engine is shut off at programmed alarm levels. A separate PC-based diagnostics program is used to read off the contents of the flashing codes.
Reading off the fault codes, and descriptions of these, are also covered with writing in the section Flash codes tables Only authorised personnel are allowed to carry out diagnostic procedures and program changes. The positions of the sensors which emit signals to the control unit are shown in the illustrations on next page. See the section How to read fault codes from the ECU control unit, for a description of how to read off flashing codes. See the section Flash codes tables for a list of flashing codes for the control unit and ECU Control unit SHOP MANUAL MT26-31 - 06.2005