Dead Caddy

Hi,

First here’s the symptom:  The car won’t start at all. Engine will not even
turn over and dash just goes black.
Hopefully someone can take the time to read this to try to understand my
problem.

SOME HISTORY THAT MIGHT HELP:
One year ago my tumbler broke with key inside. Had to drill it out. Replaced
tumbler with two new keys. Some guy
(not GM dealer) came to my house with a computer and programmed
keys. Since then it worked fine however
“Service security system” always came on and security light was on. But it
worked for the last year no problem so I
left it as is.

CURRENT PROBLEM:
About a month ago I parked the car and when I returned it would not turn
over. I immediately thought the starter
because after a few tries it started. Next day happened again but this time
for good. So I went and got a starter.
Changed it and car still would not turn over. Thinking it was a defective
starter I bench tested both and changed it
again. I got one crank out of it and then nothing. When turning the key all
goes black and nothing else.

I then saw that car seemed to think it was stuck in drive on the display so I
played with the arm a few times and
suddenly saw the light in park position. Tried it and got like half a crank and
went dead again. After doing some
Internet research, many people were saying that the “Auto Trans Manual
Shifter Shaft Retainer” which is ACdelco
part 24229611 was the problem so I got it and opened the transmission oil
pan. But piece was NOT broken. The
transmission shifts into gear without problem (P,N,R, D etc…) and when in
drive rolls forward and when in park
stops but no circle is seen on dash to show the position.

So I brought it to a local garage and they said they knew a GM expert who
could come in with machines to
diagnose. He says he finds nothing and that there seem to be no
communication happening between the
computers and he does not even see a key programmed to the car but is
also unable to program key to car or
anything. He said to check and clean all grounds. So they sanded down
and greased all grounds, still nothing.
Dash always goes black.

One last small thing Break lights remain ON all the time now also. Is this
important?

So list of what has been done:
1) Replaced starter twice
2) I checked every single fuse (engine and under seat)
3) Verified all relays and replaced relays in case that had to do with
ignition
4) Cleaned and verified all grounds
5) Dropped transmission pan and verified retainer OK

So now at a complete loss and wondering:
1) Does the security system have anything to do with it?
2) Why won’t orange circle show position of lever (PRND) especially if it’s
the security system?
3) Could computer be fried?
4) Could Transmission computer be fried? In this case would the car not
turn over anyway?
5) How can we know without just changing parts if computer is fried?

Any help or guidance would be appreciated. And if you have read this far
thanks already!