About a week ago, my own car, a 2005 Pontiac Grand Am, had the Security light come on solid while I was driving down the road for some reason. Got to where I was going and turn the ignition off, then restarted it to see if it would start. It did and the light was out and stayed out for several days. 2 days ago, parked it over night, went to start and no start. Full battery and no crank, Security light starts flashing. Okay, 10minutes with ignition in "on" position and light goes out, vehicle starts. No problems since.
I'm thinking loose wire someplace myself on mine as it just started and real intermittent. Will have to go searching if/when it does it again.
Grounds! These and several GM models are notorious for bad grounds .Will cause no stars intermittent problems.Had a Chevy Cruze a few months back they replaced ECM,BCM still same issues . Ended up being main engine ground corroded.
I was thinking the same thing, whether the "new" ECU was in working order any way.
I just got a bit more information off of him and he said the old one still works there is just issues with it. The new one I transfered the data too doesn't even start the car. It was for a friend's dad in another state so it's long gone. He just asked if I could do anything and I tried that. There must be more eeprom data in there or some other matching that must happen to get it to work.