Modes of Operation

Anytime the PCM does not apply 5 volts to the IC timing signal circuit, the ICM controls ignition by triggering each coil in the proper sequence at a pre-calibrated timing advance. This is called Bypass Mode ignition used during cranking or running below a certain RPM, or during a default mode due to a system failure.

When the PCM begins receiving 18 X reference and 3 X reference pulses, the PCM applies 5 volts to the IC timing signal circuit. This signals the ICM to allow the PCM to control the spark timing. This is IC mode ignition. During IC mode, the PCM compensates for all driving conditions. If the IC mode changes due to a system fault, the system will stay in default until the ignition is cycled OFF to ON, or the fault is no longer present. Diagnostic trouble codes are available to accurately diagnose the ignition system with a scan tool.