Powertrain Control Module

The Powertrain Control Module (PCM) is a digital computer that controls ignition timing, air/fuel ratio, fuel injector pulse width, ignition coil, spark advance, emission control devices, cooling fan, charging system, idle speed, cruise control (if equipped), tachometer (if equipped) and fuel pump. PCM sends and receives messages to other modules and the Data Link Connector (DLC) via the Programmable Communication Interface (PCI) bus circuit. For additional information on PCM, see THEORY & OPERATION - NEON & PT CRUISER article in ENGINE PERFORMANCE.