To be certain, you should:
* Consult your owner's manual: This is the best resource for the specific location on your vehicle.
* Look for a heavy-duty cord: The block heater cord is usually a thicker cord than other wires in the engine compartment. Follow the cord to find the heater element.
* Check online forums: Searching for "2001 Ford F-250 block heater location [your engine type]" on forums like Ford-trucks.com can yield pictures and descriptions from other owners.
Be careful when searching, as the engine compartment is hot when the engine is running.