Ignition Control Module: Description and Operation

The ignition control module performs the following functions:

^ It determines the correct ignition coil firing sequence, based on 7x pulses. This coil sequencing occurs at start-up. After the engine is running, the module determines the sequence, and continues triggering the ignition coils in proper sequence.
^ It sends the 3X crankshaft reference (fuel control) signal to the PCM. The PCM determines engine RPM from this signal. this signal is also used by the PCM to determine crankshaft speed for Ignition Control (IC) spark advance calculations.

The 3X reference signal sent to the PCM by the ignition control module is an ON, OFF pulse occurring 3 times per crankshaft revolution.