like micky suggests, need full model and serial number of said unit to give you accurate info.

But in general most combi units utilize steering limit sensors that do get out of adjustment and will cause issues like this. One other thing also is the wheels have stops on them to keep them from turning past their designated allowed turning points.
So if the wheel is turning around and around as you put it then i'd make sure the steering stop isn't broken or missing.
And of course check the steering sensors.
There should be 2 on the rear steer wheel and 2 or 3 on the front left wheel depending on the type of steering system is on the truck.
Regular trucks with just fwd/rev , side to side steering would only have 2 sensors per wheel. The trucks that have crab steering would have a 3rd sensor mounted mid travel of the steer rotation.