Good luck finding that one, I keep resetting mine sometimes comes back on in a month other times last about 3. could not find myself dealer wants to charge by hour to search. stays off long enough to pass inspection so I gave up looking. If u find it post were it was .:banghead:
If you just want to take a wild guess throw a gas cap at it and see what happens. More than likely it will fix it, these vehicles don't usually have to much problems with the evap system.
Here':driving:s a shot in the dark. Mine was the charcoal canister hose that runs across the top of the spare tire it came loose on the passenger side and just needed to be reconnected. I have a new gas cap if you need one only $20 from Ford!