Powertrain Control Module: Notes

NOTE: Models are equipped with an Engine Control Module (ECM), Powertrain Control Module (PCM) or a Vehicle Control Module (VCM). The difference between an VCM and PCM is the PCM controls electronic transmission internals, cooling fan and cruise control system. The VCM provides control of the engine systems as well as the anti-lock brake system. Unless stated otherwise, references to ECM and PCM also apply to VCM-equipped vehicles.

Control module is located in passenger compartment. For exact location of control module, see COMPONENT LOCATIONS in SYSTEM/COMPONENT TESTS - 4.3L article in this section. The control module consists of the Arithmetic Logic Unit (ALU), Central Processing Unit (CPU), power supply and system memories.

The control module has a "learning" ability which allows it to make minor corrections for fuel system variations. If battery power is interrupted, a vehicle performance change may be noticed. PCM corrects itself, and normal performance returns if vehicle is allowed to "relearn" optimum control conditions. "Relearning" occurs when vehicle is driven at normal operating temperature under part throttle, moderate acceleration and idle conditions.