I know this is an old thread - was the problem resolved?
I have a 4310 ehydro, and it ran fine but wouldn't move. I got code "short long long short" - supposed to be the MFWD sensor. I replaced that, didn't fix it. Turns out, it was the hydraulic oil rubber manifold collapsing. I just happened to glance at that as I was walking around the tractor at some point. The collapse was caused by me not fully cleaning the screen filter under the mid-tractor. I had cleaned it, I thought pretty well, at the last service. But when I took it back out, it had a coating of what looked like light grey paint. I used parts cleaner and a medium stiff brush to carefully clean it. Took quite a while but I cleaned until I get a lot of sunlight through it. Put it back, refilled oil, tractor works great.