4doorLX

My check engine light just came on a couple days ago and the manual says to tighten my gas cap and wait at least 3 trips to see if it goes off. Well... this was on Sat... it's now almost wed. and still on. I went to the dealership and they want $65 just to do the diagnostic. I think it was some bad gas I got, cuz I put some in a couple days prior... but I want to know for sure. Is there anything I can do without going to the service shop... like my own lil diagnostic. I'm a poor college student.. I just got my car serviced and don't wanna pay anything anytime soon for my car.

Thanks
Bran