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My Corolla's check engine light will come on then turn off after a day or two. This has happened every few weeks for the past several months. In the oil change before last I had the mechanic use MOA oil to flush the system, but the problem is still happening. What could be causing this?

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The three common problems with the variable valve control system;

  1. Low oil level resulting in low oil pressure. Looks like this has been covered.
  2. Failure of the VVT control solenoid. Test the solenoid to rule it out as the cause.
  3. Failure of the cam adjuster gears. See Toyota TSB #EG009-03 for the updated intake camshaft VVT assembly to repair the problem if everything tests good.

I have found oil additives and cleaners to be of no help with these problems.

  • Could either the VVT control solenoid or cam adjuster gears be failing sporadically? It seems like once a problem occurred they would consistently fail. – kilojoules Jun 15 '16 at 22:45
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    Solenoid coils can exhibit erratic failures that can be temperature dependent. The gear sets can exhibit all sorts or variation in behavior. They must accurately index to each other while being accelerated with rapid changes in rpm. I often wonder why they last as long as they do. – Fred Wilson Jun 15 '16 at 22:56

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