Ignition Control Module: Description and Operation

FUNCTIONS
The ignition control module performs the following functions:
^ It powers the dual crankshaft position sensor internal circuits.
^ It supplies the voltage signals that each respective Hall effect switch pulses to ground to generate the CKP Sync and CKP 1 8X signal pulses.
^ It determines the correct ignition coil firing sequence, based on 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 remembers the sequence, and continues triggering the ignition coils in proper sequence.
^ It determines 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.
^ It sends the 3X reference and 18X reference signals to the PCM. The PCM determines engine RPM from these signals.

These signals are used by the PCM to determine crankshaft speed for Ignition Control (IC) spark advance calculations. The falling edge of each 3X reference and 18X reference signal pulse occurs at a specific time in relation to top dead center of any cylinder stroke.

IGNITION CONTROL
The PCM is responsible for maintaining proper spark and fuel injection timing for all driving conditions. Ignition Control (IC) spark timing is the PCM method of controlling spark advance and ignition dwell. To provide optimum driveability and emissions, the PCM monitors input signals from the following components in calculating Ignition Control (IC) spark timing:
^ Ignition Control module (ICM).
^ Engine Coolant Temperature (ECT) sensor.
^ Intake Air Temperature (IAT) sensor.
^ Mass Air Flow (MAF) sensor.
^ Trans Range or PNP inputs from Trans Range switch or Park/Neutral Position switch.
^ Throttle Position (TP) sensor.
^ Vehicle Speed Sensor (VSS) / Trans Output Speed Sensor (TOSS).