Check Engine Light and Loose Gas Cap 2007 Accent


Hi everyone! I got a 2007 Hyundai Accent back in May. After only owning it for a little over a month the check engine light came on, I took it to the dealer and after running the diagnostic they had to replace a seal that keeps fuel from vaporizing into the air (I’m sorry but I forget what it was called)

This morning I’m on my way to work and the check engine light pops on! When I got to work the first thing I did was check my gas cap and when I opened it up I could immediately see that I hadn’t put it back on properly and the cap was starting to come off (since it’s attached to the cord)I put it back on and this time I did it tightly. I went to Advance Auto earlier this evening and when I checked for a code I kept getting an error message to try again. One of the salesguys ended up helping and when he tried it, the same message came up. He told me that normally means it was the gas cap and that because I have closed it properly it’s not reading the code any more. He then tried to earse the code, but he wasn’t able to and told me that I’ll have to go to the dealer.

I had already called this morning and scheduled to drop my car at the dealer tomorrow anyway.

My question is could the check engine light come on because the gas cap is loose even though I got gas on Sunday evening? My Accent also has a “loose gas cap” that is supposed to light up on the dashboard, but that never happened.

I’ll get my answer from the dealer tomorrow - but I am curious to know if this has happened to anyone else?

Thanks and sorry for the long story!


Yes, the CEL will come on if the gas cap is loose/undone. The light will go out after a number of cycles of starting the car–maybe 20 or so. At that point the computer doesn’t read the problem for the required period of time & the light goes out.


I forgot to say the most important part - the check engine light is still on because the guy at Auto Zone could not reset it so he told me to go to the dealer - if this is the problem that is and the CEL isn’t on for another reason.


Just for the record, the CEL can come on for many different reasons. Since some places will check the codes for free I suggest not assuming, but find out for sure.


The OBD II systems go through an elaborate check routine to verify the integrity of the evaporative recovery system. I haven’t seen a full description of the routine it goes through but one is to look for pressure build up in the tank, then a drop as the tank vents to the canister, and then it looks at the the pressure when the canister purge is activated.

On an aside, I once worked on a '96 Accent that would not complete its systems readiness checks so that it had to be referied to mass emissions inspection. Two years later it passed without a problem. Never figured out the problem.

Let us know what the dealer finds. Maybe we all will learn something.


I heard from the dealer this afternoon and it was my loose gas cap that caused the CEL to come on. They reset it - so I really hope that was the problem.


I heard from the dealer this afternoon and it was my loose gas cap that caused the CEL to come on. They reset it - so I really hope that was the problem.