3X Reference
The PCM uses this signal, from the ignition control module to calculate engine speed and crankshaft position over 1600 RPM.
The PCM also uses the pulses on this circuit to Initiate Injector pulses. If the PCM receives no pulses on this circuit, DTC P1374 Crankshaft Position (CKP) High to Low Resolution Frequency Correlation will set and the PCM will use the 24X reference signal circuit for fuel and ignition control.
For more Information regarding the Electronic Ignition (EI) System, refer to Electronic Ignition (EI) System Description.