After the dealer changed the oil and completed a transmission shift recall- check engine light comes on. After 5 trouble free years I know need a cam sensor that is "too complicated to explain " says the service manager. After researching online seems dirty or low oil can trigger this. I'm worried that either the oil change or the recall repair caused this and refused any repair from dealer. Just looking for any other advice on this. Car is mainly garaged- 5 years old with 43k miles.