Ignition Coil: Description and Operation

Coil:

The ignition coil pack contains two separate ignition coils which are controlled by the Powertrain Control Module (PCM). Each ignition coil activates spark plugs to two cylinders simultaneously. When one spark plug activates on the compression stroke, the companion spark plug activates on the exhaust stroke. During the next engine revolution, the reverse will occur.

The spark plug which activates on the exhaust stroke uses very little of the ignition coil's stored energy. The majority of the ignition coil's energy is used by the spark plug which activates on the compression stroke. Since these two spark plugs are connected in series, the firing voltage of one spark plug is negative with respect to ground, while the voltage of the other is positive with respect to ground.