2007 2.3L Blowing PCM Fuse
 

PCM fuse blows immediately with the turn of the ignition switch. The starter never starts to turn. It happened once before. Ford dealership was not able to find problem. I replaced the fuse a few times and then it just quit blowing for several months. Now it blew again and it blows every fuse that I put in it as soon as I turn the ignition key switch. I realize that there is probably a short, but need some advice concerning where to look and/or how to diagnose where the short may be.

Please help.