P0089 is a SCV Stuck Diagnostic Trouble Code on Kubota Common Rail Engines.
You cannot check anything about it without KOBD Ace Kubota diagnostic service tool.
It will not unstick itself or erase itself.
Theory:
P0089 is populated when the actual rail pressure is at least 10 mPa higher than target, for 26 seconds or more, and the discharge request value of the supply pump is below 0 mm³/st. The suction control valve (SCV) is responsible for regulating rail pressure to the common rail from the supply pump by varying the fuel flow. If the SCV is unable to control the fuel flow sufficiently this code will populate. When this code is populated, there is not a physical detection that the SCV is not moving. The trigger for the code is the actual rail pressure continuing to be higher than target rail pressure for the time specified above.
Who is "They" you keep referring to?
Do not keep running it thinking it will get better or fix itself, it will not. There are a couple of Bulletins pertaining to this failure.