I just got a code scanner for the first time after my 2012 CMS check engine light came on. I booked a stop at the dealer, knowing it was going to cost me a minimum of $80. Over the weekend I got a coder scanner (APSG for $24) and just diagnosed and fixed the issue (seal on the gas cap was bad). I am no wrencher, but this thing already paid for itself.

 

I had the same success with my gas cap issue. Pretty common fault these days with the tight emissions systems.