Why is my check engine light on?car is running great. on 2010 Dodge Charger

Had the computer read and it came up maybe a vacuum leak. My gas cap does pop off sometimes. Car is running great. This happened last summer stayed on for a week then went off. Now it came on again and don't know what the problem is.

Asked by for the 2010 Dodge Charger
5 answers 3 comments
Ok so my check engine was coming on and off, I got it read when it was on and it read cilynder 1 mis Fire. I've replaced my plenum gaskets, spark plugs, ignition coils, and sensors. Engine light came on after that, got it read again and read a vacuum leak, got that taken care of a few days ago. Check engine light just came back on. What could be the problem?
Problem with gas leak. In 2011 charger. Replaced seals, still leaks. Gas tank leaks if you fill over 1/2 tank full. Safety features will not allow you to use remote start on key fob (you can start car but it will turn off within 30sec) or to use the a/c on the recirculate position due to fumes in the cabin. Gas tank problem began with the engine light going off and on. If gas is filled over half of a tank now(use to be 3/4 full) it will leak out in front of rear passenger back tire. Heavy gas Odor coming from back of vehicle. Fumes inside car. Really bad thing is that the battery is under trunk compartment and battery lines run close by fuel tank. Unfortunately don't have the $400-$800 $$$$ to fix the problem and no Recalls at this time by dodge.
probably the gas cap is the problem, without the check engine light code its just guessing. make sure the cap is correctly installed when refueling.
I think it is something small like the gas cap because when I left the house yesterday the light was off. I have the codes and I'll post them for you when I can. Thanks so much for responding. I was happy to see the light off which makes me think it is nothing serious. :-)
SCAN CODES AND POST SO WE CAN ADV
I have the codes I'll post them for you but when I got in my car yesterday the light was off. I was happy which makes me think it is something small like the gas cap. :-)
Is it the original cap? Have seen some aftermarket's that dont fit so good. Do you know if it had an EVAP code?
Yes it's the cap that came with the car when I got it. Yesterday when I left the house my light was not on anymore. Weird but in happy. :-)