PCM "Learning Capability-
The PCM includes some learning capability that allows it to make corrections for minor variations to improve driveability. If power to the PCM is disconnected, the learning process resets and begins all over again. Most vehicles will relearn operating parameters in a short driving period. Most Scan Tools have a special test mode that can be used on some 1989 and newer models to allow the "relearn" steps.
PCM Hardware & Software
As with earlier GM systems, the PCM is divided into two main parts: the system hardware and software. The system hardware includes:
The Power Control Module (PCM)
System software includes programs that contain strategies used by the PCM to control engine system outputs based on related inputs. These are the strategies used to control the operation of the engine, electronic transmission, idle speed, fuel delivery control, and backup circuitry that is used if a major failure occurs inside the PCM.