Century V6-3100 3.1L VIN M SFI (1998)
Ignition Control Module: Description and Operation
Ignition Control Module 3X Reference Low Signal
PURPOSE
The PCM uses this signal, from the ignition control module to calculate engine speed and crankshaft position over 1280 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 will set and the PCM will use the 24X
reference signal circuit for fuel and ignition control. For DTC diagnosis refer to System Diagnosis / Diagnostic Tables / Diagnostic Trouble Code
Tables. See: Powertrain Management/Computers and Control Systems/Testing and Inspection
This is a ground circuit for the digital RPM counter inside the PCM, but the wire is connected to engine ground only through the ignition control
module. Although this circuit is electrically connected to the PCM, it is not connected to ground at the PCM. The PCM compares voltage pulses on
the reference input circuits to pulses on this circuit, ignoring pulses that appear on both.
