i got the problem with my excavator..my boom arm cannot working, cannot up and down...i already service main pump and control pump..
There is a pilot system control valve for the arm circuit. If it is unplugged or the wires are open, it can cause your problem. If the solenoid for that circuit is bad, it can also cause that problem. The coil on that solenoid should read about 25 ohms. Do you have the operation and test manual for your machine?