After a quick read of the installed PCM program with LS1edit the car cranked remained started for 1-2 secs then died. The BCM began making rapid relay actuation noise and the small red security light on the dash flashes. With the key in the ignition but off the BCM makes this noise and beeps as well. When the key is turned into the ON position the noise stop but no power is available ANYWHERE in the car. The gauges sweep but do not read.

I have replaced the BCM with another BCM and foundthe asme problem to occur.

I'm really think a PCM issue might be the problem but how did it start then die?

Any help is appreciated.

 

Sounds like the vat's system to me. Have you tried doing a VAT relearn? Did you check for any blown fuses? Just reading shouldn't damage anything. A bcm or pcm change would require vats relearn unless you disabled it in ls1edit

 

Dont think vats as the flashing and beeping is about two / sec .. only blown fuse was on the AIR pump circuit but there is not air pump inline.