Hello so I have a 2010 Chevy Tahoe and I’m getting code P0446 again after my boyfriend changed the Evaporative Emissions Canister Vent Valve and the Vapor Canister Purge Valve. Now we are trying to see what else it could be seeing this is an EVAP code. The gas cap is fine were thinking it could be the vapor Canister or the filler neck or maybe vacuum leak. It does give me a hard time when pumping gas. When fueling the pump will keep clicking off if I pump the gas in fast so I let it run in really slow so the pump doesn’t keep clicking off which takes a really long time to fill up.
That code can be caused by a blocked vent valve system.
Inspect the entire vent valve system.
It’s known that spiders laying egg sacs in this system can cause this problem.
Replace the canister. That will solve the gas fill problem. It did on my '04. While you are replacing it, blow out the vent lines with compressed air so if there are spider egg sacs in there they will clear.
I fixed a friend’s 05 Sierra by cleaning out the vent canister. Canister was packed with dirt. Truck was hard to fill with gas before, says he has no issues now. I’m not sure about codes, he doesn’t care that the cel is on, so he didn’t get them read before or after. I think the setup is a little different on the newer models, so it might be easier to just replace it.