I have a 2015 Mahindra 4540 that had 49 hours on it when the check engine light started flashing. At the same time, I also noticed a huge reduction in engine power. You can notice it when the tractor is under load, or even traveling down the road in high gear. Yesterday, it would only reach 1800 rpm when traveling in 4th high. If you are in neutral or in 3rd high, it maintains full rpm, but in the field, it drops drastically under load. I am going to change the oil in it tonight for the first 50 hour change, but I highly doubt that will correct the problem. Does anyone know what is causing this issue?
I don't have a Mahindra but if you're about to do the 50 hour service, consider changing the fuel filter. If partially clogged, the tractor runs fine without load but can't get the fuel it needs when under load. Also check fuel lines for any cracks/crimps or otherwise. If it's sucking air somewhere in through the fuel lines, you'll get the same symptoms.
Good luck and let us know how it is after your changes.