Powertrain Control Module (PCM)

The PCM controls all ignition system functions, and constantly corrects the basic spark timing. The PCM monitors information from various sensor inputs that include the following:
^ The Throttle Position (TP) sensor
^ The Engine Coolant Temperature (ECT) sensor
^ The Mass Airflow (MAF) sensor
^ The Intake Air Temperature (IAT) sensor
^ The Vehicle Speed Sensor (VSS)
^ The transmission gear position or range information sensors
^ The engine Knock Sensors (KS)

The PCM communicates with the BCM over the Class 2 serial data circuit. When the BCM enters tamper mode, it sends a Class 2 message to the PCM in order to disable the fuel injection system. If the BCM receives the expected ignition code, the BCM sends a class 2 message to the PCM in order to enable the fuel injection system. The PCM then allows the vehicle to start.