So started having problems filling up my H2 and also flashing a code P0455. Replaced the fuel cap, no difference. Replaced the vapor canister solenoid, no difference. Then replaced the evap solenoid, no difference but in doing so I found the line was contaminated with charcoal pellets. So then in goes a new canister assembly. Still no difference and still throwing the same code. I decided to try to blow the lines out. Had no issue blowing back from engine to canister but could not figure out how to blow out the line from tank to canister. This might save you some time. If you take the filler ring off (trim around gas cap) there is a vent tube that runs from the tank up to the filler neck. I disconnected that tube and basically pressurize the tank which cause the line from tank to evap canister to blow out. I got nearly a cup of charcoal out of here!!!

It filled right up with no issues after that. I will blow the lines out again after this tank but thought I would share in hopes of saving someone else grief.

Tim

 

Thanks for the post.
I'm not throwing a code, but the fuel pump clicks off & I have to fill it slowly. My neighbor with a 2012 Yukon Denali has the same issue.

I need to look into this & I'll use your approaches as a guide.

 

Code still on? after changing everything else, my code was due to the evap lines going to the top of the gas pump housing was rusted off.

 

The pump kicking off is definitely related to one of those 3 parts.

I would think that just the code could be bad line, cap or something else.

TH

 

How did you pressurize your tank

 

Take the gas cap filler trim ring off. There is a rubber hose that is attached to the metal filler neck. Remove it and using an air nozzle blow thru it. It is part of the vent system.

TH

 

Did you manage to seal it off ? I think I'm having the same thing as I've already replaced everything there is and sometimes there is that gas smell next to the drivers rear wheel as if it was leaking.

 

I had to change the fuel pump housing which comes with fuel pump. Expensive part.

 

Just did mine this weekend, top of the fuel pump basically rusts off.

 

I had this issue as well. There are 2 vents on top of the tank, one towards the front and one towards the back. I think they are referred to as roll-over valves. They are connected with a vent hose. If you put a mirror on top of the tank and climb under there you can see them.

I couldn't find a way to replace them and the dealer wanted to install a whole new tank that comes with new valves already installed. So I used some fuel-resistant sealant to seal all around my front valve. After I did this I no longer had that gas-smell when I filled up the tank. I think I posted about this a while back.