Q&A

first of all, parts stores employ parts salesman, not techs. scan tools tell you potential issues, never idnetifying bad parts.

you need a real shop with real techs to identify the real failure.

very expensive guess if they are wrong, which is very likely.

Roy

YOU SAY IT STOPPED RUNNING, IT MUST HAVE STARTED BACK UP OR YOU TOWED IT TO AUTO PARTS STORE. NO WAY TO TELL IF IT IS RUNNING OK NOW! ECU FAILURE DOESN'T "USUALLY" COME AND GO. AGREE WITH ANSWER 1 !!

You will need Chevrolet to do it for you. And it will cost you. But first, have them run a FULL Diagnostic on the Check Engine light to see if there are any hidden codes and they can tell you what is exactly wrong with the car. Also, it might need a transmission overhaul on it as well as a good tune-up. My car did the exact same thing and it needed a tune-up and the car runs a lot better. Also the spark plugs might need to be changed too with the tune-up.