DTC P1374: Crankshaft Position High-To-Low Resolution Frequency Correlation: Description

WARNING: This page does not describe the selected car, but rather 7 other vehicles, including the 2002 Pontiac Grand Prix, 2002 Pontiac Bonneville, 2002 Chevrolet Monte Carlo, 2002 Chevrolet Impala, and 2002 Buick Regal. However, it is still accessible from the selected car via links, so may be relevant.

The 3X reference signal is produced by Ignition Control Module (ICM). ICM calculates 3X reference signal by dividing the Crankshaft Position (CKP) sensor 18X pulses by 3 when engine is running and CKP sync pulses are also being received. Powertrain Control Module (PCM) uses 3X reference signal to calculate engine RPM and crankshaft position at engine speeds more than 1200 RPM. PCM also uses pulses on this circuit to initiate injector pulses. PCM constantly monitors number of pulses on 3X reference circuit and compares number of 3X reference pulses to number of 18X reference pulses and CAM signal pulses being received. If PCM receives an incorrect number of pulses on 3X reference circuit, DTC P1374 will set and PCM will use 18X reference signal circuit for fuel and ignition control. Engine will continue to start and run using 18X reference and camshaft position PCM input signals only.