Powertrain Control Module

Powertrain Control Module (PCM) is a digital computer that controls ignition system, air/fuel ratio, emission control devices, cooling fan, charging system, idle speed and cruise control system (if equipped). PCM uses input signals from various switches and sensors to control output devices in order to achieve optimum engine performance for all operating conditions. PCM contains a self-diagnostic system which stores Diagnostic Trouble Codes (DTC) if an electronic control system failure exists. DTCs may be retrieved from PCM for system diagnosis by using a scan tool. See SELF-DIAGNOSTIC SYSTEM  .