Service Engine Soon light on, any help appreciated

[fatddrfreak]

Ok, so this is my first post, but I've lurked around for a while. I have an automatic 04 g35 coupe. The Service engine soon light came on for the first time yesterday. I had just put about $40 worth of gas in the car and it was almost full. I started driving and then I noticed the ses light. I babied the car home and went online to check it out.
I read so many things about the gas cap so I checked it. It seemed tight, but I gave it a couple of clicks to see if it would tighten up. I manually cleared the light with the gas pedal. I drove the car 3 times since then, but not very far. The 3rd time I drove it, I drove to zaxby's, which is about 5 miles from my house. I waited in the drive through for about 10 minutes. I shut the car off and restarted it. About 1/2 mile from my house, and upon returning home, the service engine soon light came back on. I cleared the code again and put the gas cap back on. I havent driven it again yet.

I dont know if it just happened to do this when I got gas, and something else is wrong with the car. I see how to clear codes, but not how to read them or what not. Is there a tech article or anything that could shed some light on locating the ecu, putting it into diagnostic mode, and then going from there.
I just bought the car less than 2000 miles ago, had it service and looked at. It was a lease vehicle before I bought it. It has about 72,200 miles on it.

Any thoughts, tricks, or ideas I should know about?

Any help would be greatly appreciated.
Thanks

[pattyskin]

There are places which will give you a read-out of the code and tell you what is wrong. You put premium gas in when you put the gas in right?

[zerovdub]

I am not sure if you have any near you but Auto Zone will check codes for you for free...
I have heard that you should disconnect the battery for 24 hours due to the backup battery in the engine control modual in order to properly reset everything..

could also be
bad gas cap
water in the gas
fuel pump on its last legs
fuel pressure regulator

[fatddrfreak]

Thanks guys. Ive driven it about 20 more miles and no light yet. Ill go by autozone if it does happen again. I did put premium in. So, Ill keep you updated. Thanks so far!

[twin001]

Harbor Freight Tools - Quality Tools at the Lowest Prices

You could always buy a scan tool yourself. I bought one from Harbor Freight about a year ago and it has worked great for me. Plus, you could rent it out to friends for beer, $$$, or other favors. The one I have will also clear the codes...note, it doesn't fix the problem, just clears the codes!