Electronic Control Units

  • Important When Disconnecting Battery
    Location: Two batteries In trunk, one each behind left and right wheel housings.
    Disconnection will erase the fault memories of control units, so that fault memories must be read and, If applicable, faults printed first.
    Always disconnect both ground leads to prevent short circuits !

    Important After Reconnecting Battery
    Re-initiate front power windows: shut doors, raise windows with switches, hold switches pressed at least 3 seconds.
    Re-initiate power sun roof: close sun roof with switch, hold switch pressed at least 3 seconds.
    Checking Initiation: automatic tipping in closing direction must work. If not, repeat the procedures.

    Important With Connected Battery
    Working on components, wire connections, etc. could cause faults in the fault memories of concerned control units.
    If repairing instructions specify disconnection of the battery, this is absolutely necessary in the interest of safety.

    Windshield Wipers (Wiper Motor)
    Intermittent wiping and wipe speed 1 are switched off by an Interlock In case of disturbance.
    This Interlock remains effective even after elimination of the fault.
    Switch off the Ignition (terminals 15 and R) for 3 minutes to cancel Interlocking.


    Disconnecting the car battery will erase fault memories of the control units.
    Consequently always interrogate fault memories and, if applicable, print faults with the printer of a BMW SERVICE TESTER before disconnecting the car battery.
    The ignition must always be switched off before control unit plugs are disconnected or connected.
    Faults could be stored In the fault memories of control units with self diagnosis by removing and installing components, relays, fuses, etc..
    Consequently always Interrogate fault memories after working on the electric system. Investigate and erase stored faults.

Participate now!

Don’t have an account yet? Register yourself now and be a part of our community!