48 Reference Input - Intermittent or Noisy

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The crankshaft position sensor (CPS) defines engine position by generating an electrical pulse each time it passes by a notch of the crankshaft reluctor wheel. The reference pulse is a 5 volt square wave that switches low two times per crankshaft revolution. The PCM uses reference pulses for fuel delivery and spark timing.

Information Flag Parameters

Information Flag 48 will set if:

  • Extra or missing reference pulses are detected.
  • Time between reference pulses is too long or too short.

Diagnostic Aids

  • When attempting to diagnose an intermittent problem, use the Scan Tool to review supplemental diagnostic information. The supplemental data can be used to duplicate a problem. Select MALF History from Scan Tool EC menu.
  • Check the tightness of the female terminal grip with a spare male terminal.
  • Verify that the secondary leads are not in close proximity to the signal wires (EST, REF, etc.).

NOTICE: Information flags should be used for diagnostic purposes only. They do not necessarily indicate component malfunction/failure.