Ignition Control Module: Description and Operation

DESCRIPTION
The internal circuitry of the Ignition Control Module (ICM) will have one of two possible arrangements, push start (Gray ICM) or computer controlled dwell (CCD) (Black ICM).

OPERATION

Push Start
The push start system allows for increased dwell, or coil ON time, when starting the engine. The ICM on this system determines when to turn the coil ON based upon engine rpm information. The coil is then fired, or turned OFF, whenever a rising edge of a SPOUT signal is encountered.

CCD
The coil ON time, or dwell, for this system is thus entirely controlled by the SPOUT signal. The ICM does not internally determine when to turn the coil ON as it does on the push start system. It responds directly to the SPOUT signal it receives.

SPOUT
The Spark Output Signal (SPOUT), is a digital signal generated by the PCM providing spark angle information to the ICM. The SPOUT signal on the push start system controls only the firing of the coil. The falling edge of the SPOUT signal is ignored. The CCD system, however, does use both edges of the SPOUT signal. The SPOUT signal for the CCD system is same as in the push start except that the falling edge is now generated to control the time at which the coil is turned ON.