Ignition Control Module: Description and Operation

PCM:

The ignition control module performs the following functions:
^ Power the dual CKP sensor internal circuits.
^ Supply the voltage signals that each respective Hall effect switch pulses to ground to generate the CKP sync and CKP 18X signal pulses.
^ Determine the correct ignition coil firing sequence, based upon how many CKP 18X signal transitions occur during a CKP sync pulse. This coil sequencing occurs at start-up. After the engine is running, the module stores the sequence, and continues triggering the ignition coils in the proper sequence. If the CKP sync pulses are missing at start-up, the ignition control module is unable to determine the proper ignition coil sequence and a loss of spark occurs. However, normal fuel injector pulses occur.
^ Determine 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.
^ The ignition control module sends the 3X reference and 18X reference signals to the PCM. The PCM determines crankshaft position and engine RPM from these signals. The PCM uses these signals for ignition control (IC) spark timing calculations. The tailing edge of each 3X and 1 8X reference pulse occurs at a specific time in relation to top dead center of any cylinder stroke. The 3X reference signal is an ON/OFF pulse occurring 3 times per crankshaft revolution. The 3X reference signal is not the CKP sync pulse. To produce the 3X reference signal, the ignition control module receives the 18X CKP signal, and processes the signal through an internal divide-by-6 circuitry. If the 18X CKP signal is missing at start-up, the ignition control module is unable to generate the 18X or 3X reference signals, and a loss of spark and fuel injection occurs.