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 CKP sensor
^ The CMP sensor
^ The engine load
^ The engine speed
^ The atmospheric or barometric pressure
^ The coolant temperature

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