I have never worked on a durango but my buddy had an 05 focus that came up with an evaporative code (cannot remember which one) and after some reading found that the air line between the filler cap and the cannister next to the tank likes to plug with spiders nest (seriously, that's what I read). The solution was to disconnect at the canister and use compressed air at a low pressure to clear it. Code never returned.
Of course you are sure the filler cap is sealing right?