Circuit Description

The Ignition Control Module (ICM) sends signals that PCM requires for fuel control and spark advance calculations. At start of engine crank, ICM controls spark advance (by-pass mode). When the second 3X reference pulse is recognized by the PCM, PCM applies 5 volts to by-pass circuit, commanding ICM to switch spark advance to PCM control (IC mode). If PCM detects an open in the IC circuit, DTC will set. Engine will start and may run in by-pass mode timing.

Conditions for setting DTC:

• Engine running.
• PCM detects an open in IC circuit.