<prompt> Human: Hello PF,nbsp;I recently purchased a used car from a dealership last week. They took care of all the paperwork and the papers show the car passed emissions and wont be due for another test until 2018. I have car insurance, and did not purchase an extended warranty so I bought it AS IS.nbsp;I drove about 40 miles since then without much issue. But today, the check engine light came on. Im furious. Im wondering what I can do? Should I contact the dealership or am I SOL because Ive purchased it as is even though paperwork shows it passed emissions. The issue could be a faulty sensor or something, but I dont know enough about cars to figure it out on my own. nbsp;Any advice is appreciated.  <response>: My first step would be to take the car to AutoZone or something and have then pull the code to see what the problem is; pulling the codes is usually free. Cross your fingers, it could be something as simple as an ill fitting gas cap. 