A fault code indicating a tripped limit switch does not mean that the switch has failed. (the switch tripped so it is probably not bad). The code means that your furnace shut down because the limit switch tripped.
You need to find out why the high limit switch tripped. A blower failure, incorrect blower speed, plugged filter, too many closed or blocked air returns or registers, plugged evaporator coil or secondary heat exchanger due to the filter being removed, incorrect burner adjustment or gas pressure can all cause limit switch tripping.
Check all of the above first. The limit switch is a critical safety device, do not bypass, modify, adjust or replace it with a different switch. This can put you at high risk of a house fire or lead to a furnace failure that can cause killer carbon monoxide to leak into your house. (insurance companies can deny coverage if it is determined that a improper/unauthorized repair caused the fire)
The limit switch is located on the outside wall of the heat exchanger, usually above the burners about 8-12 inches. Your fan switch is part of your limit switch assembly or located near it. You can use your schematic to trace to the correct switch. Your fan switch will have a adjustment (fan off temp), your limit switch may or may not have one, if it does DO NOT ADJUST IT. Again, the switch itself is usually not the problem.
If you provide more details about your problem and the sequence of events that lead to the furnace coding out we may be able to provide more help.