i just got my a4 quatro 2.8 like 3 weeks ago and i was driving 2 work 2day and my check engine light came on so all day at work i was just browsing online cause it was bugging the crap outta me cause i like my stuff 2 work right and i was wondering what possible reasons u think it was !! i asked my dad he said it might have been if the gas cap was left very loose which it was when i just checked and im still gonna have it checked and every thing and still runs the same but i was thinking it was a o2 sensor or something or this seems very common with this car from what i saw online tell me what u think cause i dont know cause im used 2 drive a nissan 300zx tt and this never happened 2 me