Powertrain Control Module & Vehicle Control Module: Notes

NOTE: Models are equipped with a Powertrain Control Module (PCM) or a Vehicle Control Module (VCM). The difference between 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. References to PCM also apply to VCM-equipped vehicles, unless stated otherwise.

For location of PCM/VCM, see COMPONENT LOCATIONS in appropriate SYSTEM & COMPONENT TESTING article. The PCM consists of 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 is interrupted, a vehicle performance change may be noticed. PCM module 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.