Ignition Control Module: Description and Operation

DESCRIPTION

Ignition Control Module (ICM):

The Ignition Control Module (ICM) receives engine position and speed information from the Crankshaft Position (CKP) sensor, and desired spark advance information from the Powertrain Control Module (PCM).

OPERATION
The ICM uses the information from the PCM to determine which ignition coil to fire, calculating the turn ON/OFF times of the ignition coils required to achieve the correct dwell and spark advance. It also synthesizes a Profile Ignition Pickup (PIP) signal and an Ignition Diagnostic Monitor (IDM) signal for use by the PCM. In addition it sends information on system failures through the IDM signal to the PCM and stores information for Diagnostic Self Tests. The IDM also provides the signal for the tachometer.

Failure Mode Effects Management
During some Electronic Ignition (EI) system concerns, the Failure Mode Effects Management (FMEM) portion of the Spark Output (SPOUT) from the PCM ICM will maintain vehicle operation. If the ICM does not receive the SPOUT from the PCM, it will automatically turn the ignition coils ON and OFF using the CKP signal. However, this condition will result in fixed spark timing (10 degrees BTDC).

Ignition Diagnostic Monitor
The ignition diagnostic monitor (IDM) is a function of the ICM. The ignition control module sends information on system failures to the PCM, which stores the information for diagnostic self tests. The IDM signal is also used to drive the vehicle instrument tachometer and/or test tachometer for diagnosis.