Ignition Coil: Description and Operation
Six Tower Coil Pack (Stand Alone ICM Only):
The coil is turned ON (i.e. coil charging) by the Ignition Control Module (ICM), then turned OFF, thus firing two spark plugs at once. One is for the cylinder which is to be fired (on compression stroke) and the other goes to the mating cylinder which is on the exhaust stroke. The next time the coil is fired the situation is reversed. The next pair of spark plugs will fire according to the engine firing order, etc.