CEL light and code

In addition to the fuel tank itself, the filler neck, fuel pump gasket, etc. there are also the components of the evaporative system including the charcoal canister, various valves and solenoids and the hoses connecting them. There can be a leak at any point that will set a code. Exactly what components you have and where they are depends on what model car you have. Unfortunately, small evap leaks can be difficult to troubleshoot. Sometimes the only way to find them is with a smoke machine which means a trip to a shop.

I might start with a simple gas cap replacement. I'd be willing to bet it's the most likely cause for an evap sensor to trigger.

On a semi related note, my last vehicle failed emissions here in IL because of it and all it needed was a new gas cap. THey test the gas caps independently which, one would reason, is because they are frequently a problem area.

Best Regards,

-- Todd H.