2002 Nissan Altima owners only

My “service engine soon” light came on 2 weeks ago. Because the tire kicks a lot of stones and water into the drainage hole just beneath the gas cap, there was a lot of buildup of rust on the metal part the gas cap screws onto, so I carefully sanded it down (after talking to the dealer). The light stayed on for several more days, so I also replaced the gas cap with a new one in case the rubber seal was too worn out with all the rust—however, the problem still remains.

Here’s my question: I think that the place where the fuel hose is inserted used to have a spring-loaded metal flap. I checked, and it certainly isn’t there anymore, if it ever was (what I remember is that after unscrewing the cap, you would see a flap covering the hole, and then insertion of the fuel hose into the tank would temporarily push it down).

Could someone please do me a big favor and check to see whether they have a flap covering their fuel tank opening? Also, while you’re at it, do you have a guard covering the drainage hole (directly beneath the screw-off gas cap). I noticed it on the 2006 models, but mine doesn’t have it.

I don’t own an Altima, but I can tell you for a fact that the presence or absence of the flap would not set a service engine soon light. There is no flap sensor.
You could have set the light from a number of different things, a loose or not sealing gas cap being one of them.
Different cars have different stratigies for turning off the light once it has set. I should note the light will only go off if the condition has been corrected, if the lght is for something other than a gas cap issue, it is not going to go out, from you dinking around with the filler neck, and replacing the gas cap.