Powertrain Control Module (PCM)

The PCM is responsible for maintaining proper spark and fuel injection timing for all driving conditions. Ignition control (IC) spark timing is the method the PCM uses to control spark advance and ignition dwell. To provide optimum driveability and emissions, the PCM monitors input signals from the following components in calculating IC spark timing:
^ The Crankshaft Position (CKP) sensor
^ The Camshaft Position (CMP) sensor
^ Engine load
^ Engine speed
^ Atmospheric or Barometric Pressure (BARO)
^ Coolant temperature

There is one circuit between the PCM and the IC module. This circuit is called the ignition timing signal and is by the PCM to command the IC module to trigger the coil.