Ignition Control Module: Description and Operation

DESCRIPTION
The main function of the Ignition Control Module (ICM) is to switch between ignition coils and trigger the ignition coils to spark.

OPERATION
The ignition control module receives the Profile Ignition Pickup (PIP) and Cylinder Identification (CID) signals from the crankshaft position sensor, and the Spark Output (SPOUT) signal from the powertrain control module. During normal operation, PIP is passed on to the powertrain control module and provides base timing and rpm information. The CID signal provides the ICM with the information required to switch between the ignition coils for cylinders 1 and 4 and the ignition coils for cylinders 2 and 3. The SPOUT signal (from the contains the optimum spark timing and dwell time information. The spark angle is determined by the rising edge of the SPOUT signal because that is when coil current "turns off" and spark occurs. The dwell time is controlled or varied by varying the duty cycle (duration) of the SPOUT signal. Current flows in an ignition coil (dwell) when SPOUT is "low". This feature is called Computer Controlled Dwell (CCD). Therefore, with the proper inputs of PIP, CID and SPOUT the ICM turns the ignition coils on and off in the proper sequence for spark control.