Ignition Control Module: Description and Operation

The Electronic Ignition (EI) module monitors the CKP sensor signals and based on these signals, sends a 7X reference signal to the PCM so that correct spark timing and fuel injector control can be maintained during all crank and run conditions. Since the PCM controls spark timing and ignition control during crank and run, there is no bypass mode.

This system uses the same circuits between the ICM and the PCM that distributor type systems use. Following is a brief description for each of the IC circuits.
^ Crankshaft Position (CKP) sensor activity (7X reference) - The CKP sensor generates a signal to the EI module which results in a reference pulse (square wave signal) being sent to the PCM. The PCM uses this signal to calculate crankshaft position, engine speed and injector pulse width. The engine will not start or run if this circuit is open or grounded.
^ Reference Low - This wire is grounded through the EI module and insures that the ground circuit has no voltage drop between the EI module and the PCM which could affect performance. The PCM compares voltage pulses on the 7X or reference input to those on this circuit, ignoring any pulses that appear on both. A pulse that appears on the reference low circuit alone is assumed to be caused by Radio Frequency Interference (RFI).
^ Ignition Control (IC) 1 & 2 The PCM sends the ignition control pulse to the EI module on these circuits. These signals are similar to the 7X reference pulse square wave except that the PCM uses sensor inputs to determine the pulse timing to control spark advance. When the PCM receives the 7X signal, it will determine which pair of cylinders will be fired (1 & 4 or 2 & 3). It then tells the EI module which cylinder to fire through the ignition control circuits.