320 B cat excavator bogging

trying to figure out why it bogs when working it.Checked volt at PVR unplugged the wire have 53 volts with switch in manual And 48 when in auto with key in on position book says should have 24 volt.Also checked the wire for ground it has continuity book says should be 0. Green light is on on the controller any ideas on this have code 4103 which says proportional is ground circuit is open.

320 B cat excavator bogging