Circuit Description

WARNING: This page is about a different car, the 2003 Pontiac Grand Am, 2003 Oldsmobile Alero, 2003 Chevrolet Monte Carlo, and 2003 Chevrolet Impala. However, it is still accessible from the selected car via links, so may be relevant.

A 3X reference signal is produced by the Ignition Control Module (ICM). The ICM calculates the 3X reference signal by dividing the Crankshaft Position (CKP) sensor 7X pulses by 2 when the engine is running and the CKP synchronizing pulses are being received. The Powertrain Control Module (PCM) uses the 3X reference signal to calculate the engine RPM and the CKP at engine speeds above 1600 RPM. The PCM also uses these pulses to initiate injector pulses. The PCM compares the 3X reference pulses to the 24X CKP pulses and the Camshaft Position (CMP) pulses. The engine will continue to start and run using only the 24X CKP and CMP sensor signals. If the PCM detects an incorrect number of pulses on the low resolution engine speed signal circuit, DTC P1374 sets.