Eng. Fault code PO446 Evap. System need Help.

[BKLYNH2]

Thanks for all the replies guys. I should have a better idea after this weekend is over. Interestingly both ideas have credibility. I once had a very catastrophic fuel overspill but I also reinstalled the original gas cap shortly thereafter which since I hadn't been using it for 3 years was in new condition. I think that Humtech is probably right on and Rox's comments really help confirm that. I have beat the crap outta my truck over the years and driven through a lot of junk, mud and water. The effects of this are appearing everywhere these days. I will have a look at the evap canister and components tis weekend and maybe someone can tell me which parts need to be replaced when I report back.