Here, we’re diagnosing an intermittent misfire symptom, caused by an excessive crankshaft position sensor air gap. “Trash in, trash out” is how the saying goes, and this video is a perfect example. I’m also demonstrating the power of a lab scope, and the importance of verifying signal inputs before replacing parts.

Engine Performance Diagnostics chapter 21 page 20

symptoms 50

  • intermittent misfire
  • no codes present

fix 50

  • adjust crankshaft position sensor air gap

test shown enh 50

  • using an in-line spark tester to check for an ignition system issue
  • checking an ignition coil primary current waveform with a lab scope and low amp probe
  • checking camshaft and crankshaft position sensor waveforms for faults
  • checking an ignition coil control signal (transistor external of the PCM)
  • manually checking a crankshaft position sensor air gap

Tools used

  • in-line spark tester
  • Picoscope automotive 4 channel lab scope
  • inductive low amp probe

end faq

Playlist

(Chapter 21) Ignition inputs, cam and crank sensor

Related videos:

Hall effect cam/crank sensor operation and testing Part 1 (an SD Premium video):

Hall effect cam/crank sensor operation and testing Part 2 (an SD Premium video):

How to test a crank sensor (Chrysler Dodge Jeep):

Faulty cam sensor setting a crank sensor code - P1389, P0320, P0622:

end faq


For more information on this topic, I have written a “field manual” called Engine Performance Diagnostics which is available as an eBook or paper book.

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