Gosh I know this is going to sound stupid and I don't mean for it too, but did you make sure that your gas cap was tight after your fill-up? If the cap is not tight (it has to click for it to be tight), this can cause the Emission Control System to signail a false system malfunction and throw up the CEL. I am not overly sure about what codes it would possibly throw up though. Maybe someone else can elaborate on this further if they think it is the cause and has happened to them in the past.
Just thought I would throw that in for good measure!
