The "check engine" light on my car was on for a week and a half prior to my appointment, and it coincidentally turned off the day of. However, the technicians were still able to assess what was wrong - a loose seal - and fix the problem in a timely manner. I was very hesitant to bring my car back to SMP because, previously, I had simply been told that "there was nothing wrong" with my car and it ended up having the turbo and transmission completely replaced! It was good to see that they changed their attitudes even though it wasn't a big problem.