cardoc

Good evening
If your car had a passlock antitheft problem the engine would not crank.The interm.no start problems are always tough,you get it to a shop with a scanner and of course it starts no problem.The trick is to diagnose the problem whiles it's happening.If the no trouble codes are stored my bet is on the crankshaft position sensor.Somewhat of a common GM problem-see previous posts.Other no start issues without codes could be fuel pump or relay,ignition switch contact etc.What do you do to get it started when there is a problem?Does it try to start like it just ran out of gas just crank over dead. My gut still tells me crank sensor.
Good luck/keep me posted.
Cardoc