First check the relay, which I believe you did. Then the pump for operation, and yours works. Then check the valve itself, and if you don't have a way to command a test, I'd just remove it and actuate it by hand (you can remove the top portion from the piping, I think it's torx screw but I can't recall), using some carb cleaner in the valve while opening and closing it.
If the valve is just stuck (from what I've seen they're more often stuck than dead), the carb cleaner and forced actuation should free it up. If you see rust (moisture does accumulate in the piping around the valve just like the exhaust), you can even try something like PB Blaster or any other penetrating oil and do the same thing, opening and closing it by hand. Basically the same thing as freeing up a stuck EGR valve. If you use penetrating oil, clean it out with the carb cleaner after to remove as much residue as possible, and let it dry completely before reinstallation.
If the valve works and moves freely, there is a gasket where the piping connects to the exhaust manifold. A leak here will set off codes.
Something else to keep in mind, exhaust leaks can and will set off this code, even if the O2's aren't being affected much. The reason I say this is because I have an exhaust leak somewhere around my upper manifolds (I can smell it in the engine bay and more recently in the car, and hear a ticking on acceleration), and I have the P0411 code. I've ruled out every other problem and am certain that's why I have the code, so it wouldn't hurt to check for exhaust leaks.
A very easy way to find exhaust leaks it to stuff some rags into your tailpipes and start the engine with your hood open. Obviously you don't want to run it like this too long, but the back pressure created by the rags will make any exhaust leaks you have MUCH more audible and usually can be felt by placing your hand around the area you hear it. Just be careful not to touch the manifolds of course, they get hot almost instantly.
