Note. For circuit reference, see DTC P0300 schematic.
Circuit Description
IC module creates a 4X signal and a 24X signal that is used by the PCM for ignition and fuel control. In this test, PCM checks for 4X reference pulses being received without 24X reference pulses. When engine is running and PCM is receiving 4X pulses without 24X reference pulses and the 24X reference signal line is low for 4 seconds, DTC will set.