never had a problem til now. 45,000 miles and always up on maintenance. I dont seem to notice a problem and it runs great. My check engine light is on and two seperate dealers show the code as Emissions control. Ive had my gas cap replaced, and had a sensor put back on it that had popped off. Its been looked at twice since then and the light isstill on, two dealers cant figure out whats wrong with it. Advice?