Starter not working

Replaced transmission. Pulled motor and all out. Put new transmission in motor etc. All wires plugged in and grounds checked and triple checked. No crank over. Can cross the starter will turn over no run. All fuses checked and triple checked all are good. Battery is in tip top shape. Starter pulled and tested for extra measure tested good. Turn key to "on" lights come on and stay on, security light goes out (PKIII system), security light does after a few minutes with key left on "on" beeps three times and stays on, Did run a relearn process five times no change. Turn to "start" no crank starter fuse relay clicks no run. Ignition relay is eight volts good the same for starter relay. I am at a loss any help would be great.

Update:
plugged in a scan tool and theres no comm to the PCM Or the BCM, testing the pinouts on the PCM will update later.

PCM tested bad but was a false bad, Replaced PCM with a exact match no go. Currently its in a shop now still waiting on a answer.

Turns out its so stupid, the main wire connector on driver side fender under the hood was backwards. Problem solved

Why 2001 lesabre wont start. Battery, alternator and starter is good.

Initially the heater would not come on. All the control lights indicates it's on. Heater would not work in auto and could not get the fan to come on or outside vent air even. I checked the fuses and could not find anything amiss. This is when the real trouble started. I went to start the car and Nothing. The dash lights come on but the solenoid/starter doesn't even click. I jumped the battery but nothing. The whole heater story may have nothing to do with it but could could a relay be the problem? I called AAA club and they came out. Same thing, jump did not help. Dead silence. He checked the battery. It's Ok and he did a simple continuity check and it appeared that power was getting as far as the fuse box. Any ideas before I have the car towed to a Dealership? I swapped out the few 10 amp fuses that I initialy touched but still nothing and again maybe it's coincidental.
Thanks,
Dennis

My 2001 buick la sabre won't start, the radio and a/c come on, what could it be?

2001 Buick Lesabre 6 cyl Automatic 160000 miles

Hi, I've been driving a second-hand lesabre for a year and a half now and have not really had engine problems, until now. I've had three window motors go out, but that is something I can live with right now. My engine not starting, on the other hand, is something I can't.
I was driving to work today and when I got out, I heard a sound coming from the front. It sounded like a belt turning or something like that. I popped the front open, but didn't see anything wrong. There was a slight burning smell. I tried to start my car, but I turned the key, and it wouldn't even turn over the start. The brake locked up and nothing happened. It's been a little harder to start it recently, but nothing like this. I let the car sit for a bit and came back to look at it. There were no sounds, but when I put the key in to start it, it wouldn't turn and the belt sound came back on. Help, please?

I backed it out of my driveway and, having forgot to get soemthing in the house, turned it off. When I tried to start it again, I could hear a click near the key, but lights do not dim and engine does not turn over. Battery was checked but is fine. One person suggested it has something to do with the key or Theft Deterrent system. Any advice?

My apologies for mistyping, but lights do NOT dim. I will give your suggestions a try.