Ignition Control Module: Description and Operation

Electronic Ignition (EI) System With Ignition Control (IC):

The Ignition Control Module (ICM) performs several functions:

^ It powers the 3X crankshaft sensor circuit.
^ It determines the correct ignition coil firing sequence, based on 3X pulse. 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 a "3X crankshaft reference" (fuel control) signal to the PCM. The PCM determines engine RPM from this signal. It is also used by the Powertrain Control module (PCM) to determine crankshaft position for ignition control spark advance calculations. The signal sent to the PCM by the ICM is an "ON-OFF' pulse occurring 3 times per crankshaft revolution.