Powertrain Control Module (Pcm): Notes

All models except E46 use an 88-pin PCM. See Fig 1. E46 models use an PCM with 9-pin, 24-pin, 40-pin and 52-pin connectors. See Fig 2-Fig 5 . For PCM location, see PCM LOCATION  table. PCM uses intake airflow, intake air temperature, throttle position, coolant temperature, engine speed, vehicle speed, crankshaft position, knock sensors and exhaust gas oxygen content intake signals to determine optimum fuel injection and ignition timing.

Fig 1: PCM Connector Terminal Identification (E36, E39 & E38)

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Fig 2: Identifying PCM 9-Pin Connector (E46)

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Fig 3: Identifying PCM 24-Pin Connector (E46)

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Fig 4: Identifying PCM 52-Pin Connector (E46)

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Fig 5: Identifying PCM 40-Pin Connector (E46)

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PCM can operate engine in a limp mode, allowing vehicle operation despite component failure. PCM also has adaptive capabilities to compensate for component wear and other factors, such as minor vacuum leaks. Once a fault is recognized, it is stored in PCM memory as a Diagnostic Trouble Code (DTC). The system automatically substitutes a fixed replacement value for the incorrect value caused by a defective component or circuit.

An air/fuel ratio of 14.7:1 is maintained under most driving conditions. Maximum engine RPM is limited by PCM by eliminating power to fuel injectors. The PCM assumes control of following functions: