Been chasing evap issue. Pretty sure this is the problem. This line appears to go from the top of the filler neck to ?????

I have so many questions. Why does it just dead-end into mid air? Obviously it used to connect to something, but what? I would assume it should go into the charcoal canister but it isn't facing that direction at all.

Also is there a complete diagram of the evap system anywhere?

In California EAP issues are a big deal because if they give a code, you cannot re-register your vehicle.

Years ago my Honda pilot there was a known issue with a pair of O-rings at the transition from the metal gas filler pipe to the rubber hose going into the fuel tank. A tiny vacuum leak at this joint O-rings caused a CEL to light up. I spent days studying all the components to finally solve the problem with these O-rings. Fortunately, I was able to disassemble the connection and I greased it heavily and reassembled and it worked.

The charcoal canister is a important part of a proper functioning system. There's usually solenoid valves and all kinds of other complexities.

You're right that dead ending line looks incomplete. Hopefully someone will know what it's about.

Looks like the line is "Fuel Tank Breather Tube Sub-assy"

I guess this lets air escape while filling.

Sadly there is no access to it, so unless anyone has ideas I guess the truck is going to a shop with a lift.