I wouldn't worry too much about it for the time being. The light comes on when there is a smog related issue and usually doesn't effect driving or safety at all. You may be producing more emissions but you can drive thousands of miles with the light on. I'm sure others will chime in to the contrary but thats my experience. The port is there as others have said and it probably has a cap over the opening and it has to be accessible for testing. Did you have a loose gas cap? If so it may take several cycles to clear although I'm not sure they have a sensor for that on the F53.