If a malfunction occurs in the ignition and fuel injection system while driving, the defect is stored in the control unit. When the engine is off, the defect can be recalled from memory using a BMW service tester connected to the diagnostic connector (right in the engine compartment), and eliminated. It is therefore advisable to have the fault memory interrogated at a BMW workshop regularly, even if no faults appear to have been observed.
Short circuits, breaks, excess enrichment values or incomprehensible functioning are stored as defects. In this case, a stored defect may be a failure of the element, the corresponding wires or the control unit. In addition, the frequency of occurrence of a stored defect can be derived from the memory.
Ignition voltage control circuit at low ignition voltage disables the DME system, the engine cannot be started. This avoids damage to the catalyst.
Attention: If the battery is disconnected or the ECU connector is disconnected, the data in the memory is erased.
Rules for cleanliness when working on the fuel injection device
Thoroughly clean the connection points and their surroundings with petrol.
Put the removed parts on a clean lining and cover. Use film or paper. Do not use rags with lint! Install only clean parts.
With an open system: If possible, do not work with the compressed air system. If possible, do not move the car.