Hello, I am sorry no one could help you earlier. Unfortunately, I don't have much good news for you either.
The only way to troubleshoot this engine is to connect to the ECM. Most AG machines do not have an interface to the monitor and without anyway to view the diagnostic fault codes, you can only throw money at it until you find something that works.
You can look on the engine for damaged or loose connectors and maybe get lucky. Beyond that, you will need to call a CAT dealer to view all the codes.
I would recommend you ask for the Forestry and AG group first as their service rates are much lower than the Power Systems group you normally call for Industrial engines. Hopefully you have one of these formerly Pioneer dealerships close to you.
This is a Perkins designed engine, you may have some luck with any code reader that works on trucks and equipment J1939 protocol. Much of the service codes shown in the manual reference the SPN number that is a generic J1939 code. I do not know of any tool that does work, I just have heard some others can do this job. I use CAT ET program but, it is licensed and expensive for a single use.
If you have a tool available, check for codes and post them here with the full engine serial number and I may find something to help you repair this problem.
I will OPT-OUT as I am only available at night. I can OPT-IN if you need me