On my 2555, once the MIL light is set, it goes into limp mode and limits the engine power output. [ just like your 5555 ] My tractor still has the factory flash from early last year, and I am waiting for my dealer to get an upgrade EGR kit to put on it. To clear the EGR codes, and shut off the MIL light.... you have to start and run the tractor three full work cycles. Not just start it and run it for a few minutes... shut it off, then start again. The few times I have had it happen, I just put a code reader on it and clear the EGR codes... and that usually shuts the MIL light off. If it does not work, you can unhook the negative battery cable for a few, then that should clear it. Mahindra knows about the problem and has worked out a fix according to what I have heard. They are working on the EGR kits for the 2555, and help is coming. I would contact your dealer on the 5555, and get him in the loop.