Hi All,
have a 2015 suburban LT, I have changed the charcoal canister, changed evap canister and vacuumed out all the lines as well as blew air through them. However the gas pump will still click and there about 1 gallon. I have read the the return line vent in the filler hose can et clogged leading to this but after I spend 20 minutes filling up the rich bank 1 & 2 codes come up. Not sure what the issue could be but let me know what you guys have experienced.

 

Only thing I think would cause this is that return vent line you mentioned.

 

Was thinking that or maybe I received a bad vent valve so will try to pressurized the vent valve line from the charcoal canister slightly to see if it will vent before ordering the filler vent hose. 1 thing i didn't mention was that those little charcoal ***** made there way to the top of the engine going up the purge valve lines

 

If all the evap has been checked and replaced. Fuel pump is going or (unfortunately more than likely) high pressure fuel pump. Lines on it are one use as well. Thanks to the GM engineers.... it is under the intake manifold. Older chevys also had this issue but with fuel pressure regulator, also under intake.