I have been reading these threads for awhile and know that it is all good stuff. A really solid site! I am posting because I need help! I have a Komatsu pc 120-5. It is a great machine and everything looks and runs great. Except for the fuel control dial, which throttles the machine up. It does not work. I have installed a new governor motor and a new fuel control dial switch. It did not solve the problem. I have tried to troubleshoot a lot of different areas, nothing works. Anyone have this problem? I'd appreciate some feedback. Thanks!
Behind the seat and under the jockey box there are a couple of doors that flip out unless your machine is a gray market. If you look straight down on the open doors with the key on one of the doors will have three light emitting diodes, the two outsides are red while the middle one is green. The other door will have a red light diodes that will spell out a letter, a flashing dot if the engine is running and then a number. It will look like this S.2. The three diodes are the diagnostics for the engine control computer while the letter number door is the diagnostics for the hydraulic pump control computer. Let us know what you see and we can help you from there.
I will check the lights when I get back into the shop on Monday! The computer box flashed 2 codes, and 18 and a 25, which have something to do with and MVC solenoid. I had a Komatsu tech come out and he claims the governor controller box is bad. I took that off and it looks like the circuit board is fine. He seems to think there is power going into the box, but nothing coming back out. I'm not so sure and I need a few opinions before I drop another 2 grand on a new one!