Code P0455?
 

EVAP leak? cant seem to find it, even after new gas cap. anyone have this code come up? i have about 195,000.00 miles

Under a minute to search Google and look.... All kinds of information out there. Searching is your friend.
https://www.google.com/search?q=humm...obile&ie=UTF-8

i should have been more specific, i'm trying to find a diagram of the fuel evap system for a hummer 3 2006 so i can start by trracing the tubes and connections....

Most likely the Vapor Canister Vent Valve; pretty common failure on these and the Colorado/Canyons. Dorman part # 911-070. I replaced mine after trying a new fuel cap. It only took me about an hour to do the job. No more EVAP code. You're welcome and good luck.:D

thnks chimpy ;)

https://cimg7.ibsrv.net/gimg/www.hum...c90f79f824.jpg

https://cimg3.ibsrv.net/gimg/www.hum...3f731a4aa0.jpg
https://cimg9.ibsrv.net/gimg/www.hum...f2cc35c43b.jpg

this diagram is a great help, i couldnt find it on my online manual. is it possible to test the purge valve first before replacing it or replace the vent selenoid first?

I just replaced the vent canister on my 06 H3, 99K miles. P0442 code is now gone. Get some PB blaster for the one bolt. I even sprayed the rusty metal clip that holds the canister. As for the hose; I could NOT pull it off. I ended up using channel locks to smash the old canister's hose fitting, then the hose slipped right off.

Edit= this is the one I bought
https://www.amazon.com/gp/aw/d/B001KSCSQU?psc=1&ref=yo_pop_mb_pd_title