according to the code chart the code 29456 is a sensor fault.
the 4 possible failures are:
1-speed sensor/motor controller connections/wiring
2-speed sensor failure
3-motor controller(s) failure
4-motor failure

first i would check the lights on the display and see which ones are lit telling you which system is at fault, it will either be the drive or hydraulic. Those pict-o-graphs are a motor with a gear inside it with a number 1 or 2, or a motor with a cylinder inside it.
Then you will know where to start looking.
Check for loose or damaged connections at the motor connections on the motors and on the controller(s).
If that checks ok then check the motor(s) associated with the system shown on the indicators on the display, the speed sensor may be faulty.
Otherwise if no issues are found then it ultimately may be a faulty controller.