Anything that could cause a misfire will turn this light on. Have the spark plugs ever been replaced? If not that would be the first place to start. You may not feel a misfire, but it could be that tha plugs or coils are getting weak and not firing as hard as it should. Denso plugs are the best spark plugs for this vehicle. Other brands have been known to turn on the check engine light.
Sorry I do not see a reply, but it says you did reply. Is there any other questions yuo have?