Attention: Each control unit is programmed for certain basic parameters, which are only average values. The control unit receives from sensors different input values, depending on the state of the engine, which are compared with the values stored in the unit. In accordance with these, the control signals of the block are changed. The new values are remembered, which corresponds to "learning process".
If the DME control unit has been without power for more than one hour (unit removed or battery disconnected), then the self-learning system loses the stored values.
When reinstalling a block with erased information or when installing a new block, the system must remember the input values again. This process can cause engine roughness and engine braking disturbances. In order to compare all parameters of the state of the engine, it is necessary to drive the car for several minutes at a variable speed.
Withdrawal
Before removing the control unit, it is recommended that a BMW Service Center interrogate and print out stored faults. This determines the type of defect.
Switch off the ignition. Disconnect the ground wire from the battery.
Attention: When the battery is disconnected, the information in the electronic memory devices, such as the engine trouble memory or the radio security code memory, is erased. Disconnect the battery only when the ignition is switched off, so as not to damage the fuel injection system control unit. When disconnecting the battery, follow the instructions in sections "Radio" And "Removing and installing the battery".
If the battery is located in the engine compartment, remove the battery.
Release the 3 upper spacer clips by pulling out the clip rod with a screwdriver and then the clip itself.
Loosen the 2 lower plastic nuts, see illustration. Remove rubber cover.
Loosen 3 screws and move cover with cable harness to one side.
Swing out the retaining clip of the connector and remove the connector.
Pull the control unit out of the mounting brackets. It is not necessary to unscrew the mounting bracket bolts.
Note: With an automatic transmission, another control unit is located above the DME control unit.
Installation
When purchasing a new unit, indicate the number of the control unit and its coding. It is recommended to bring the removed control unit with you.
Push in the control unit. Connect connector. Close retaining clips.
Place overlays.
Install battery.
If the control unit has been de-energized for more than 1 hour, or if it is a new unit: Warm up the engine to operating temperature. Carry out a variable speed test drive for approximately 10 minutes. At the same time, the control unit "studies" engine parameters.