How to test Intake Valve Control Solenoids (codes P0028, P0082) - Subaru

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

Fix
- added 2-3 quarts of oil to the crankcase

Tests shown
- 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 flow charts suck

Tools used
- incandescent test light
- scan tool
- lab scope
- digital multimeter

Playlist
- (Chapter 3) Transistors, Solenoids, Computer Controlled Output Testing youtube.com/playlist?list=PLE9BA8CBD51B8C48E

Related videos
- Honda VTEC System Testing (P1259 trouble code)
youtu.be/vTis29MQC4U
- How to test a computer controlled solenoid (power/ground side identification) youtu.be/kQz3g4HIWgs
- Intake/Exhaust Camshaft Actuator Solenoid test (P0010, P0011) - GM 2.4 youtu.be/_RF4yct8J54
- How to test cam/crank actuator solenoids (P0010, P0013) 2008 GM 2.4 L youtu.be/6B7HrBN2tvY

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