Ignition Coil: Description and Operation

Three twin-tower ignition coils are individually mounted to the ignition control module. Each coil provides spark for two plugs simultaneously (waste spark distribution). Each coil is serviced separately. Two terminals connect each coil pack to the module. Each coil is provided a fused ignition feed. The other terminal at each coil is individually connected to the module, which will energize one coil at a time by completing and interrupting the primary circuit ground path to each coil at the proper time.


The ignition control module performs the following functions:

^ It determines the correct ignition coil firing sequence, based on the sequence of 7X crankshaft position sensor pulses. This coil sequencing occurs at start-up. After the engine is running, the module remembers the sequence, and continues triggering the ignition coils in proper sequence.

^ It determines whether or not the crankshaft is rotating in the proper direction, and cuts off fuel delivery and spark to prevent backfiring if reverse rotation is detected.

^ It sends the 3X reference signals to the PCM. The PCM determines engine RPM from this signal. This signal used by the PCM to determine crankshaft speed for Ignition Control (IC) spark advance calculations. The falling edge of each 3X reference signal pulse occurs at a specific time in relation to top dead center of any cylinder. The 3X reference signal sent to the PCM by the ignition control module is an ON-OFF pulse occurring 3 times per crankshaft revolution. The PCM calculates the 3X reference signal from the 7X crankshaft position sensor.