Need help with emissions code

[YukonXL04]

Hey guys, so I have hade code P0449 on my truck for a while now haven't cared but now it's time for state inspection and I need to pass... so I have replaced the gas cap, evap solenoid by the gas tank and the purge valve on the intake... still have the dang code. Any one have any ideas? I'm guessing next step to trace all the evap lines and look for leaks? I don't have means of activating the solenoids unless someone can tell me what to check with a multi meter.

Edit: I also had p0455 but changing the one on the intake got rid of that code.

Thanks for any help

 

[YukonXL04]

Update: purge valve on intake is working properly, it's controlling vacuum via PWM. I have good vacuum down to the charcoal canister. If I unhook the vent and tank evap lines from the canister I have good vacuum at those ports. My problem is if I hook up the tank line and leave the vent line open, I get no vacuum on the vent port which leads me to believe my tank isn't holding vacuum.

I have traced all lines at the tank and none have any obvious likes if leaking IE cracks or worn spots. So going from here how do I check for a leak on the tank hoses for vacuum?

If it were pressure that's easy with soap and water. But with vacuum it won't blow bubbles.

Any help appreciated.

 

[ccapehartusarmyINF.(ret)]

I spent 6 months wrestling with that freakin evap system i eventually just replaced it all the purge valve solenoid (on top the intake) the vent valve solenoid (above the rear diff) the gas cap all the hoses keep in mind the drive cycle conditions for the evap system test especially hotter climates ill prolly be like a month or two so its gonna take time before you know if what you did fixed it fortunatly the evap system causes no driveability issues

 

[YukonXL04]

Final update. If anyone has the vent solenoid code, check your 4ws fuse under the hood. Apparently the vent solenoid under the truck gets power from the 4 wheel steering fuse regardless whether you have quadrasteer or not...

So after finding that out and putting a fuse in, my evap codes are gone and has successfully pass inspection

 

[ccapehartusarmyINF.(ret)]

haha thats good to know
so the vent solenoid the one above the rear diff runs off the the same fuse as quadrasteer even in vehicles without you should post a picture of were the fuse is at

 

[YukonXL04]

Yea it was a tough one. I had searched before for any evap fuses but this one didn't come up until I searched for evap wiring diagrams.

Here is the pic. This is the under hood fuse box. Circled in red

Also here is the evap system info and troubleshooting.