We have a similar problem. Ours will just stop and if you shut it off and go away it will start working again. Hydraulics work but will not move. Frustrating as Cat dealer doesn't seem to have procedure to diagnose problem. Manuals have been lost. Have done a lot of work to it lately so that it would be reliable. Have seen where it could be accelerator controller but any suggestions would be helpful.

Please let me know If you found the problem, I have the same situation except I have to turn wheel all the way right to go forward and all the way left to back

Thanks.

I will try to reach the sensor and check/clean connections, but there is not schematic.
Is there any chance I could get it
Thank you very much for your help.
Yiannis.

if you have or had travel when turning the steering full left or right but not anywhere in the center that sounds like a problem with the sensor board that is mounted on top of the steering axle underneath the control panel.
the 2nd thing that comes to mind would be the directional contactors or the logic card , possibly some connection issues there but if the motors were turning in fwd and reverse when turned left or right then that leads me to think something wrong with the steering position sensor board.
Try running the onboard diagnostic and see if it will pass the steering angle sensor test (test 5).
Hopefully the schematic is still underneath the hood, if so it has all the instructions on how to do the onboard diagnostics.
make sure you remove the drive fuse before the test, it will tell you to if you dont ;o)