Ignition Control Module: Description and Operation

SYSTEM IMPUTS
- The Ignition Control Module (ICM) receives a signal from the Crankshaft Position Sensor (CKP). During normal operation, CKP signal is sent to the Powertrain Control Module (PCM) from the CKP and provides base timing and RPM information.
- The Camshaft Position Sensor (CMP) signal provides the ICM with the information required to synchronize the ignition coils in the proper sequence.
- The Spark Output (SPOUT) signal is sent from the PCM. The SPOUT signal contains the optimum spark timing and dwell time information.


OPERATION
- The Spark Angle is determined by the rising edge of SPOUT. This rising edge is when ignition coil current turns OFF and spark occurs. The dwell time is controlled by varying the duty cycle (duration) of the SPOUT signal. Current flows to an ignition coil (dwell) when SPOUT is low. This feature is called Computer Controlled Dwell (CCD). With the proper inputs of CKP, CMP and SPOUT signals, the ignition control module turns the ignition coil ON and OFF for the proper sequence of spark control.

IGNITION DIAGNOSTIC MONITOR (IDM)
- The IDM is a function of the ICM. The ICM sends information of system failures to the PCM. The PCM stores the information for use during diagnostic test mode.
- The IDM signal is also used for vehicle instrument tachometer and test tachometer for systems diagnosis.