troubleshooting a hitachi ex 100-2 electical issue

My hitachi excavator hydraulics went into limp mode and now the dealer is telling me I have to hook it to a laptop in order to figure out what is wrong with it??

I have service manuals for the machine but nothing is in them about troubleshooting electrical issues or how to go about testing for problems.

Has anyone made a "test" harness before in order to figure out what is going on, or where can I buy a laptop to hook up myself along with the harness's to hook to the laptop??

My pump...

troubleshooting a hitachi ex 100-2 electical issue

troubleshooting a hitachi ex 100-2 electical issue