I'm lookin into buying a used car. There's one that seems to be a pretty good deal, but apparently the Check Engine light is on, and the guy says it's due to a faulty gas cap. Now I don't know much about cars at all, and I Googled and couldn't find what I needed...so is this a relatively serious problem? Costly fix? Will it effect MPG? Or would you just move onto the next vehicle?

This happens in a lot of cars from what I have heard.

^^^ This. I would go with the guy to the service place and make sure before you buy it, have them look at it.

GM cars that have OEM 2 need the engine system to be pressurized in order to run right. A loose or non sealed gas cap will cause the check engine light to come on. Take the car for a test drive and while on the test drive take it to Autozone and have them pull the engine codes for your answer if that is the real reason. I believe they will pull your engine codes for free.

Correction OBD 2 not OEM 2. My automatic correction changed that on me and I didn't notice.

Thanks for the input...goin to see it tomorrow and will swing by Autozone.

My 1997 Lumina had 147,000 miles when I got it in August of 2005 and the check engine light was on.

The check engine light stayed on till it hit 185,000 miles then went out so I figured it burnt out.

At 195,000 miles it came back on and is still on to this day at 205,000 miles.

Chesapeake wrote: My 1997 Lumina had 147,000 miles when I got it in August of 2005 and the check engine light was on.

The check engine light stayed on till it hit 185,000 miles then went out so I figured it burnt out.

At 195,000 miles it came back on and is still on to this day at 205,000 miles.

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Could have not reset the ECM after service or the car ECM is telling you that a oil change is needed