1990 DeVille not starting

[pithi69]

So the anti-theft light always flashing is normal?

I noticed something today, if I hooked up the two yellow wires going to the starter relay together, the car will turnover but not start. Seem's like its not getting any fuel. It will start for a second and turn off.

[maxwedge]

That's because your are bypassing the Vats. On cranking, 12v at the yellow wire into the PRnDl switch ,12v on the purple out. This comes from the starter enable relay. PM me your email address I can send you a basic starter wiring diagram.

[pithi69]

Okay, I finally figured it out. After all that time. I know this thread is old but I want to let people know what was wrong with my car for their own experiences.
So I almost replaced everything. It wasn't the following:

Ignition
Ignition Switch
Ignition Control Module
Starter Relay
Starter
Battery
Alternator

It was simply the VATS Control Module. Which is located behind the glove box, mounted behind a relay panel. All that happened was that the connector plug for the vats module had moisture sitting in it causing some of the pins to corrode and break.
All I did to repair this was to take some same diameter welding wire and solder it into place, plug it back in and the car fired up with no problem.
ALL THAT EXTRA WORK FOR NOTHING. So if you are stumped that your GM is not starting and you think its something to do with the VATS, check the module. Most likely 95% the reason your car is not starting.