So several months ago I changed the timing belt on my girlfriends 09 Aveo with the VVT engine. Well just about a week ago we got a check engine light and I pulled the code. It said slight advance in exhaust Cam. Didn't have any issues til now. I put it in TDC and pulled the top timing cover an the dots pointed towards each other. Started the car and the check engine light was gone. An today it came back on saying the same thing. What gives?