daisy turtle

I have a 2005 mustang with a V6 in it and he sprayed down my engine bay and cleaned it, I got 2 miles down the road and my baby died! Called and had the car trailer brought and took it to my mechanic and he can't get the computer to communicate with the code reader. Anyone else have this problem, am I gonna have to buy a whole new computer for my car? Half afraid to ask about the quote on this repair!!