My excavator a KOMATSU PC 300-6 is not swinging left or right and it is shutting off the engine?

Well ... your excavator's hydraulic system runs psi in excess of 5,000 lbs. This excavator has built in safety switches designed to turn systems off-line if it detects trouble. This avoids a catastrophic leakage that could be lethal to driver and/or nearby personnel.

Any number of reasons temp, hydraulic,or mechanical breakage. Sounds like foreign matter/dirt entered this system keeping the system relief valves from operating? All individual pumps/cylinders needs to be checked and system purged/cleaned by system tech or mechanic.

en.wikipedia.org/wiki/Komatsu_Lim….

Go to "heavy equipment forums " join and ask the question there heavyequipmentforums.com.

You've told me what its doing but I'd really need to physically diagnose your machine to determine what is causing your problem, your talking about a piece of very complex heavy equipment here, not a common motor vehicle, this thing makes your Lexus look like a tinker toy, Don't try and fix this yourself, Bad Things Will Happen if you don't know what your doing, Yes there is a reason Heavy equipment mechanics make more than other mechanics, they have to know a lot more.

I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.