Ford Repair: 1999 Escort, power supply sources, battery cables

Question
"I have a 1999 Ford Escort, 2.0 liter SPI, auto trans, 87000 miles. Recently, I had the ECM replaced by a dealer, because the MIL was on for a heated oxygen sensor. They checked the 02 sensor and circuits and said they were ok, and that the problem was the ECM. After they replaced the ECM, the car started to die out randomly. I drove the car about 2100 miles, in varying conditions. When the car dies out, I scan it and it shows 5 monitors as incomplete.(I/M Readiness) No codes or pending codes are present. The last time it died, I had the scanner recording the data. When the car died, with the key still in the run position the scanner said, "Error, unable to communicate with vehicle". When I got it restarted, the recording continued as usual. . I was wondering if the new ECM is bad?   If I hook up(back probe) a volt meter to the + and - lead at the computer harness and it shows voltage when the scanner shows the message, "cannot communicate with vehicle" ..Does that mean the ECM is bad??? Or any other ideas???"

Answer
could be bad ecm although factory ones don't give much problems they are getting worse-also since it is clearing every time(no monitors set and no comm) look and battery cables power and ground
especially ground on engine side, find wiring diagram and check all power supply sources.