Ignition Control Module: Description and Operation
DESCRIPTION AND OPERATIONAll functions of the ignition control module are contained in the powertrain control module. The Ignition Control Module (ICM) receives the Crankshaft Position Sensor (CKP) signal from the CKP sensor. It processes the CKP signal into Profile Ignition Pickup (PIP) information and transmits it to the Powertrain Control Module (PCM). The PCM processes the PIP signal along with signals received from the Throttle Position (TP) sensor, Mass Airflow (MAF) sensor, Heated Oxygen Sensor (HO2S), Engine Coolant Temperature (ECT) sensor, Octane Adjust (OCT ADJ), barometric pressure sensor, Vehicle Speed Sensor (VSS), and Brake On-Off (BOO) switch according to a spark advance map programmed into the PCM. The PCM produces a Spark Output (SPOUT) signal which it sends back to the ICM. Using the SPOUT and CKP information, the ICM switches primary current to the ignition coils among the three ignition coils and provides the optimum amount of spark advance and dwell. The ICM module also sends back to the PCM an Ignition Diagnostic Monitor (IDM) signal which the PCM uses to indicate a failure mode and which is also used to provide an RPM signal to the instrument panel tachometer.