What do you mean “just a toss up?” If you were to look in the Ford diagnostic manual or used the search function on here for code 513 you’d find this answer from a couple weeks ago.


“Replace processor” seems pretty cut and dry to me.

 

It's worth checking the capacitors on the computer circuit board. Here's the thread where I replaced mine.
Relay chatter after turning key off - Ford Truck Enthusiasts Forums https://www.ford-trucks.com/forums/1...g-key-off.html