Powertrain Control Module (Pcm): Notes

WARNING: This page does not describe the selected car, but rather 10 other vehicles, including the 1994 GMC Yukon, 1994 GMC Suburban, 1994 GMC Pickup, 1994 GMC Cab & Chassis, and 1994 GMC C3500 HD. However, it is still accessible from the selected car via links, so may be relevant.

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 TESTS W/CODES article below or under COMPONENT LOCATIONS in appropriate SYSTEM/COMPONENT TESTS - GASOLINE article in the ENGINE PERFORMANCE section. 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 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.