Powertrain Control Module (Pcm): Notes

NOTE: Most models use a Powertrain Control Module (PCM) instead of an Electronic Control Module (ECM). The only difference between an ECM and PCM is the PCM controls electronic transmission internals and cruise control system in addition to electronic engine controls. Unless specifically stated, references to ECM in text and diagnostic flow charts also apply to PCM-equipped models.

On most vehicles, PCM is located in passenger compartment. For exact location of PCM, see ECM/PCM LOCATION in TESTS W/CODES article or COMPONENT LOCATIONS in SYSTEM/COMPONENT TESTS article in this section. The PCM contains the Arithmetic Logic Unit (ALU), Central Processing Unit (CPU), power supply and system memories.

The PCM has a "learning" ability which allows it to make minor corrections for fuel system variations. If battery power to PCM is interrupted, a vehicle performance change may be noticed. This will correct itself and normal performance will return if vehicle is allowed to "relearn" optimum control conditions. This is accomplished by driving vehicle at normal operating temperature, under part throttle, moderate acceleration and idle conditions.