hitachi ex 120-2 electrical issues please help

I am in desperate need of some help on my machine. I have a hitachi ex120-2. that the throttle is not working. on. i am getting 15 volts and sometimes 25 volts to the 2 power legs of the ec motor. when i hook the ec motor up the throttle will jump from power to off and keep repeating. we have replaced the control pad, the ecu, the cab harness,also a new ec motor. if anybody has had any problems like this or has any ideas please help. thank you