Disconnecting & Connecting ECM/DME Control Module

Disconnecting vehicle battery will cancel fault memories of control units. Before disconnecting battery, always read out fault memories. Investigate stored faults and, once any faults have been remedied, cancel fault memory. Control unit connectors should only be connected and disconnected while ignition is turned off. Removal and installation of components, relays, fuses, and other components can cause faults to be stored in fault memories capable of self diagnosis. Always interrogate fault memories after completing work on electrical system. Investigate stored faults and, once any faults have been remedied, cancel fault memory. If replacing ECM, always read out hardware/software version of corresponding control unit with BMW DIS tester. Comply with instructions of DIS tester for coding and programming.

On vehicles with electronic vehicle immobilization, follow instructions of DIS tester. Each control unit is programmed with certain basic values, which serve as mean values. Control unit receives different input values, depending on engine condition, which are compared with stored values. Adaptive system compares input values with stored map values. Control commands are routed to relevant actuators. If, for example, DME control unit was without current for a long time (more than an hour), its adaptive system would lose stored values. When a cleared control unit is restarted or a new control unit is installed, adaptive system must read and store input values of associated engine as new basic values. If not performed, this could lead to erratic idling and disturbed overrunning of engine after starting. Depending on engine, it could require some time before all values are adapted to engine condition.

Observe following procedure before replacing or reinstalling a control unit: If possible before exchanging control unit, run engine up to operating temperature. Remove control unit. Install a new control unit and operate vehicle at different engine speeds.