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

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(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:


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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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On ScannerDanner Premium I will bring you right into my classroom at Rosedale Technical College. You will find page for page lectures taken right from my book as well as exclusive classroom type case studies. What is so special about these classroom case studies? I pull live problem vehicles directly into my classroom and we troubleshoot them in real time, using and applying the theory and testing procedures we learn during the classroom lectures. There is no better on-line training of how to troubleshoot automotive electrical and electronics systems anywhere!