not accessible?

i have had this problem of the service engine soon light coming on after about five minutes of driving but when you shut it off and start it again it goes away and comes back. so i took it to a local garage and he hooked the computer to it and it said not accessible he said there was something wrong between the computer and the pcm on the car any tips or pointers on figuring this out so i can get rid of the service engine light ohh.... and reset my abs so it works

A lot of places don't know they need an OBD-I scanner to scan your 1995. They probably were trying to use an OBD-II scanner, because their cable fit the DLC under the dash. It's not going to communicate with the wrong scanner.