Mustang Blown EEC Fuse

I have a 1998 Mustang Gt with 87,000 miles that died in traffic with no warning. Flashing anti-theft with a crank no-start (PATS can't communicate with EEC). The EEC fuse blows immediately after the key turns to the ON position. Short is still present after EEC is disconnected. Short disappears when the Constant Control Relay Module is disconnected so I put a new one in but the short is still there. A mechanic has spent hours going over the car and has found no bare wires anywhere. Mechanic has given up. Any ideas would be greatly appreciated. I am about ready to scrap this car because I have already spent hours of head scratching and hundreds of dollars in the garage trying to have it fixed.