Ignition Control Module: Description and Operation

PURPOSE
The ignition control module (ICM) uses information to direct which coil to activate and to calculate the "turn on" and "turn off" times of the ignition coils, which is required to achieve the correct dwell and spark advance. This is determined by the ICM when it receives information on engine position and RPM from the Crankshaft Position (CKP) sensor, and desired spark advance information from the Powertrain Control Module (PCM).The ICM also generates a Profile Ignition Pickup (PIP) signal and an Ignition Diagnostic Monitor (IDM) signal for use by the PCM.
The ICM sends information on system failures through the IDM signal to the PCM; the PCM stores the information for Diagnostic Self Tests. A Clean Tach Output (CTO) signal is also provided to drive the tachometer.

FAILURE MODE EFFECTS MANAGEMENT
During some electronic ignition system faults, the Failure Mode Effects Management (FMEM) function of the ICM will maintain vehicle operation. If the ICM does not receive the Spark Output (SPOUT) input from the PCM, the ICM will automatically activate the ignition coils "on" and "off" using the CKP signal. However, this will result in fixed spark timing (ten degrees BTDC).

IGNITION DIAGNOSTIC MONITOR
The Ignition Diagnostic Monitor (IDM) is a function of the ICM. The ICM sends information on system failures to the PCM and the PCM stores the information for diagnostic self tests.