Powertrain Control Module (Pcm): Notes

NOTE: Some models use 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 PCM also apply to VCM-equipped vehicles.

PCM is located in passenger compartment. For exact location of PCM, see PCM LOCATION in appropriate G - TESTS W/ CODES article below or under COMPONENT LOCATIONS in SYSTEM/COMPONENT TESTS article in the ENGINE PERFORMANCE section. The PCM consists of the Arithmetic Logic Unit (ALU), Central Processing Unit (CPU), power supply and system memories.

TESTS W/CODES - 2.2L (for S10 Pickup)
TESTS W/CODES - 4.3L (for all others)

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 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.