No crank no start

I have a 09 pontiac g6 2.4l.  A few weeks ago a p0128 tc showed up suggesting i may need a new thermostat.  Figuring it would be ok to drive it for a while since it wasn't an overheating issue I put it off. A week later I noticed that the ac wasn't working and that my temp gauge bottomed out.  Found out that's a safety measure.  However, the gauge would start working intermittently and everything would be fine.  One day the gauge completely stopped.  I started the car drove one place, started it again, drove it to another, started it a third time no prob.  The 4th time, after i stopped for gas,  no crank with "error" on the odometer.  I know my starter turns when i jump the relay,  but Im not getting bat voltage in crank.  Ive pulled off every ground except the one behind the ac and cleaned them. Nothing. I pulled off the tps to measure a ref v. I got .70. What else do i need to do?

Start unplugging the 5 volt reference sensors or cutting the wires at the pcm to eliminate sensors and wiring. Need to check power and grounds at the pcm to

I'd want to check communication with the ECM/PCM. If you don't have communication with that, do you have communication with anything else? That'll help narrow your search.

Does the check engine light come on when you turn the key on? 

Which wire at the TPS were you checking, exactly? Here's a shot of the throttle, for reference:

 

There is no check engine light. It showed .71v at the purple wire key on. .002 key off. I have a cheap scan tool and it says no comm. There is a ground behind the ac compressor that i can't get to yet but I don't know if that's the computer ground.

Check the power feeds to the pcm. No light and no comm, that's where I would start. Did someone work on it? How are the UBEC's in these(asking other techs as I retired in 08 and we had quite a few failures)? Just check all the fuses under the hood.