Circuit Description

Ignition Control Module (ICM) produces 18X reference signal. ICM calculates 18X reference signal by filtering Crankshaft Position (CKP) sensor 18X pulses when engine is running and CKP pulses are also being received. PCM uses this information to calculate engine speed and CKP at engine speeds less than 1200 RPM. PCM compares number of 18X reference pulses to 3X reference pulses and Camshaft Position (CMP) pulses. DTC will set when, PCM receives incorrect number of pulses or no 18X reference pulses are received in one engine cycle (720 degrees of crankshaft rotation).