Operation

The PCM uses reference pulses from the CKP sensor in order to determine engine speed. The PCM cannot operate the ignition system (or the fuel injectors) without the engine speed signal from the CKP. The PCM controls ignition timing by controlling the ignition coils.

Each ignition coil has a built-in ignition module that controls the current flow in the primary coil winding. When the current flow is interrupted, the electrical field around the primary coil collapses and a high voltage is induced in the secondary coil. The secondary coil voltage travels from the coil output terminal, through the spark plug boot, and across the spark plug gap to the engine block. As a fail-safe function the ignition control module sends an ignition confirmation signal back to the PCM whenever the primary field collapses.

The CMP sensor input is used to detect engine misfire. The PCM also uses the CMP sensor signal as an input for modifying fuel injection timing and modifying ignition timing.

The PCM receives information on engine status from various engine sensors and then selects the most appropriate ignition timing settings from within the PCM's programming. The following are the most important inputs for determining ignition timing requirements:
^ Engine speed
^ Throttle position
^ Intake air volume
^ Engine coolant temperature
^ knock sensor input