18X Reference PCM Input

The PCM uses this signal from the ICM in order to calculate the engine RPM and the CKP at engine speeds of less than 1200 RPM. The PCM also uses the pulses on this circuit to initiate the fuel injector pulses. If the PCM does not receive pulses on this circuit, DTC P0336 sets and the PCM uses the 3X reference signal circuit for fuel control and for ignition control. The engine continues to start and run using the 3X reference signal.