Self-diagnosis. General description (BMW 7 Series E32)

Engine management systems installed in BMW vehicles are mainly produced by Bosch and include the following systems: Bosch Motronic versions 1.1/1.3; 1,2; 1,7; 3,1; 3.3 All BMW engine management systems control the primary ignition circuit, fuel system and idle speed from a single electronic control unit.

Self-diagnosis function

Each electronic control unit has a self-diagnostic capability, in which it constantly monitors signals from certain sensors and engine actuators and compares each signal with a table of programmed values. If the diagnostic software determines that a fault is present, the control module stores one or more fault codes. No fault codes will be stored if there are no codes for faults in individual components or for conditions not covered by the diagnostic software. Depending on which control system is installed, the control unit will output either two-digit or three-digit fault codes, so the appropriate fault code readers must be used to read them.

Bosch Motronic 1.2 system

Early BMW VI2 engines are equipped with a Bosch Motronic 1.2 system with two electronic control units. Each control unit is assigned to a bank of 6 cylinders (ECU 1 to the right bank, and ECU 2 to the left bank) and collects data from its own sensors. Each ECU stores its own fault codes and must be serviced independently of the other.

Limited operation mode

The BMW vehicle systems discussed in this chapter use a fail-safe function. When certain faults are identified (not all faults trigger the limited operation mode), then the electronic control unit starts the limited operation mode and will be guided by the programmed values, and not by the signals from the sensor. This allows the car to safely reach the place of diagnostics and/or repair. When the malfunction is eliminated, the control unit will return to the normal operating mode.

Possibility of adaptation or "training"

BMW systems also use an adaptive function that modifies the basic programmed values for the most efficient operation under normal conditions and to compensate for wear on engine components.

Self-diagnosis system indicator lamp

BMW models are equipped with a CHECK ENGINE warning light installed in the instrument cluster. Error codes indicating faults in components related to the exhaust system can be read by flashing the warning light.

The self-diagnosis plug is intended only for use with the trouble code reader and is located in the engine compartment on the left or right fender, or near the engine compartment bulkhead, or near the suspension strut.

(The original source of the article is on the website: bmwman)