Computers and Control Systems: Service and Repair

12 00 ... - Notes/information on removing and installing control units

Important!

- 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.

- Control unit plugs should only ever be connected and disconnected while the ignition is turned off.

- The removal and installation of components, relays, fuses etc. can cause faults to be stored in fault memories capable of self diagnosis. Always interrogate the fault memories after completing work on the electrical system.

- Investigate stored faults and, once any faults have been remedied, cancel the fault memory.

- If necessary, initialize power window units

When replacing the DME/DDE control unit, observe the following:
- In each case read out the hardware/software status of the relevant control unit using the BMW diagnosis system.

Comply with the instructions of the DIS diagnosis system on the steps pertaining to coding and programming.

On vehicles with electronic vehicle immobilization, comply with the instructions of the BMW diagnosis system.

- Each control unit is programmed with certain basic values, which serve as mean 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. The control commands are routed to the relevant actuators.

- If the DME control unit is without current for a long time (more than one hour), its adaptive system loses the stored values. When a cleared control unit is restarted or a new control unit is installed, the adaptive system must read in and store the input values of the associated engine as new basic values itself.

- 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.

- Therefore observe the following procedure before replacing or reinstalling a DME/DDE control unit:

1. If possible before exchanging control unit, run engine up to operating temperature.

2. Exchange control units and run the vehicle at alternating engine speeds.