1996 Tacoma ECM shuts down, please help

I have a 1996 Tacoma that will start and run great then after a few minutes of driving the engine light comes on. I have tried to connect it to the computer and it read link failure. The port has worked in the past so I know its not the problem I have read codes before and replaced parts. The fuse is good. The computer stops communicating with the truck. If the AC is on when the ECM fails the compressor also stops running and the engine has poor performance, (air flow/ gas mixture) so this lets me know that the ECM looses total communication. I have went use other scanners and have has the same outcome. When reading some of the forums some issues are caused by a loss of ground. So before i go purchase a ECM I wanted to see if anyone has had this same problem before.

Thanks In Advance