Operation

The PCM uses reference pulses from the CMP 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 CMP.

The ignition coils supply spark to 2 engine cylinders, and spark plugs, at the same time. When the PCM signals the ignition module to interrupt the current flow in the primary coil windings, the electrical field around the primary coil collapses and a high voltage is induced in the secondary coil. The secondary coil voltage travels simultaneously from both coil output terminals, to the spark plugs, and across the gap of each spark plug to the engine block. The CKP sensor signal is used by the PCM for engine misfire detection.

The PCM controls ignition timing by controlling the ignition coils. The PCM receives information on engine status from various engine sensors and then selects the most appropriate ignition timing settings from within the programming of the PCM. The following are the most important inputs for determining ignition timing requirements:
^ Engine speed
^ Throttle position Manifold pressure
^ Engine coolant temperature