03 Yukon has code PO 449

I understand this has to do with the evap canister solenoid valve. Is this a "parts changer" fix and if so where do I start? I have looked all over (and under) for any system leaks. We have very destructive pack rats here that will chew anything so that is always my first thought. Thanks, I appreciate any guidance.

Welcome to AF, an issue with the evap cannister vent solenoid bad/ disconnected or hoses to and from it a problem

Thanks for the prompt reply. I have been all over this thing (2003 Yukon XL, 5.3L Flex) looking for damaged or leaking hoses, etc. I then called the GM dealer parts dept and was told I needed a evap purge valve at about $136, which is a special order. I asked what other vehicles it would fit thinking there would be many. IE: All GM 1/2t trucks, Escalade, Suburban etc. Parts boy admitted to a couple, EXT and maybe Escalade. I then called the Chevy dealer parts. They looked up by my vin# and sold me an evap canister solenoid ($28)
I was so happy until I got home and could not find the part anywhere on my vehicle!! I expected to go right to it underneath on the frame rail near the canister and fuel tank. Not so! HELP, where the heck is this thing?? Is it a part only used on some but not all of the trucks? I am so confused and facing emissions test prison.
Thanks

Find the evap cannister it is attached to the top of it.