Fuses are settings on the controller board they do various things such as set clock speeds, bootloader options, brownout detection etc.
You would need a chip programmer to change these settings (assuming it's an avr.. avr tiny, avr dragon, JTAG ice etc) I wouldn't mess with these settings it's not like you can change them without the programmer!

I'd look for a wiring fault .. issue a M119 command to check your endstops open/closed state.. then hold the switch in and issue it again, this will tell you if your controller can see the switch.

You could also plug in one of the y or z switches and try and stop the carrige manually.