Engine Control Module: Service Precautions
Removing and Installing Electronic Control UnitsCAUTION:
- Disconnecting the vehicle battery will cancel the fault memories of control units. consequently, before disconnecting the car's battery, always interrogate the fault memories. Investigate stored faults and, once any faults have been remedied, cancel the fault memory.
- Ignition must always be switched off before disconnecting or connecting control-unit connectors.
- the removal and installation of components, relays, fuses etc. can cause faults to be stored in fault memories capable of self diagnosis. For this reason, fault memories must always be interrogated after working on the electrical system.
- Investigate stored faults and, once any faults have been remedied, cancel the fault memory.
Please note when replacing DME/DDE (Digital Motor Electronics/ Digital Diesel Electronics) control unit:
- In every control unit, certain mean values are stored which illustrate the basic values.the control unit receives different input values, depending on engine condition, which are compared with the stored values. the adaptive system compares the input values with the stored map values. Appropriate correction commands are sent to the concerned drive elements.
- If, for example, the DME control unit were without current for a long time (more than an hour), its adaptive system would lose the stored values. After re-commissioning a cancelled unit or installing a new control unit, the input values of the relevant engine must be read in and stored for the adaptive system.
- This procedure could lead to erratic idling and disturbed overrunning of the engine after starting. Depending on the engine it could require some time before all values are adapted to the engine condition.
- The following procedure is therefore to be noted before replacement and/or re-installation of DME/DDE control unit takes place:
- If possible before exchanging control unit, run engine up to operating temperature.
- Remove the control unit, install a new control unit and operate vehicle at different engine speeds.