On this system the intake valve lift is varied by two different cam lobes. A low lift lobe and a high lift lobe. I misspoke in the video calling this a variable valve timing or VTEC mechanism. This system does not vary cam timing, but it does vary intake valve lift. What was unusual with this fault was when you have "circuit low" type codes, this is almost always an electrical problem to the solenoid or the solenoid itself is open. However everything tested fine electrically and we found that this engine was very low on oil. Once we added oil, these codes did not return.

Engine Performance Diagnostics chapters 2 and 3

symptoms 50

  • check engine light (P0028, P0082 codes)
  • poor performance

fix 50

  • added 2-3 quarts of oil to the crankcase

test shown enh 50

  • how to identify oil switching solenoid valve circuit design
  • how to identify variable valve lift pressure switch circuit design
  • how to test both the solenoid and pressure switch
  • why manufacturer flowcharts suck

Tools used

  • incandescent test light
  • scan tool
  • lab scope
  • digital multimeter

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(Chapter 3) Transistors, Solenoids, Computer Controlled Output Testing

Related videos:

Honda VTEC System Testing (P1259 trouble code):


How to test a computer controlled solenoid (power/ground side identification) :


Intake/Exhaust Camshaft Actuator Solenoid test (P0010, P0011) - GM 2.4 :


How to test cam/crank actuator solenoids (P0010, P0013) 2008 GM 2.4 L :


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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!