This was my mothers car and runs great when it starts. This car will start great and then out of the blue it will not even turn over. All the idiot lights come on and you turn the key and nothing. Come back and try it again 10 min. later and it starts up like there was never a problem.
I am new to the forum and need feed back on this before I replace the ECM or is it a security problem with the fob, I replaced the batterys in both fobs and still have the problem. You never know when this car wants to start.

try wiggling the shifter or putting it in park. could be nuetral saftey switch. does it have to be later or can you try the ign a few times and have it work?

could be the start enable relay too, you can test to see if you are getting the enable ground on the yellow

I had 96 Buick park avenue. It did the same thing and sometimes quit when driving. On the Buick it was the crank sensor. You might wanna try that.

A bad crank shaft position sensor would not stop an engine from turning over. It would crank without starting.

Oh sorry i missed read it.

First thing I did was go from Park to N and back again to no avail/. When this happens I find that if I keep trying to start it the car never starts. If I leave it alone for 10 - 15 min and lock and unlock the doors with the fob and talk nice to it most of the time it starts. It seems always when I need to be somewhere it does it then the not so nice talk.
Nice schematics, thanks. The starter enable relay will be the first thing to be replaced.
Seems like it could be a hand full of different things to make this car act like this. I sure appreciate the feed back and thanks for taking the time!

check that wire labled y from the pnp if you have a ground on there with your key and stuff in there you know you are good with the pnp and vats.