I have a 2000 Cavalier that starts up then shuts off 3 seconds later. I have no security light on dash at all (cluster needles work but no lighting for night driving). I tried the leave ignition on 3 times in 30 minutes method but to no avail. I think it might be a bad ECM. Could it be a bad computer, passlock 2 ignition lock cylinder , bad instrument cluster? I just installed a new ignition switch but still the same. I feel like I am running out of options. The car has been parked since January. Three weeks earlier I replaced the cylinder head and then it drove for 3 weeks, and that was all.
Thanks for any suggestions Scotty.