Hey old post but i found the solution in a different forum. Guy said the original GM cam sensor solves this start issue. He said randomly no start on 1st crank but ALWAYS starts on 2nd crank..... im having this issue after i installed a Delphi SS11368. He said he went to a junk yard and found one with GM 12561211 stamped on it, and it works perfectly now. Im going too try it as well

 

In the past, I replaced the cam sensor a couple of times. Finally ensured it was GM and all was well. Not too long ago it started throwing a related DTC. I can’t recall which number. I replaced it again and the code disappeared. So apparently the cam sensor is a weak link in this. Thanks for replying and confirming.