So turns out that "flashing" check engine light while driving was caused by 1 or 2 bad fuel injectors... i went ahead and replaced all 6 of them. It drove smooth and natural. No transmission issues, no codes, nothing. The next morning (this morning) i get out and run some errands and the light came back on but it was saying that the thermostat was stuck open on the code. So i tore it down and replaced the thermostat. Good to go, back to stress free driving. Or so i thought.... out of nowhere, my connection for the fuel pressure regulator started loosening and i began to lose fuel pressure. I patched it up with a few zip ties and its running good again. But boy i tell you, when i say "one thing after another" i wasnt kidding...

Ummm . . . fuel pressure [anything] held on by zip ties is a recipe for an engine fire down the road.

I know that, I’m grabbing a new figment today, it was just a temporary fix until I figured out where to get another one

Okay cool. I figure if you didn't know then this tells you, and if you did know, at least it got mentioned for others that might read this and not know.

Lost communication is usually down to the data wiring somewhere being broken or intermittent. Especialy in relation to CANbus.

That said, there also isn't anything preventing a bad body/engine bay ground from letting the modules in question actually power on. Of course, they can also be powered on and not communicate due to the data not being able to reach the PCM or DLC connector.

As far as the body module, I would check your cab ground wire. I dont own a envoy, so I have zero direction for where the ground wire could potentially be located.

The PCM not having comms, well now that MIGHT be the best place to start. Are you absolutely 100% positve you have more than 12.5VDC at the battery?
Working from the battery, are you 100% sure you have the same 12.5 or more at the underhood relay box? The leads going to the bigger fuses in these underhood relay boxes are prone to corrosion and greening, just as bad if not more so than the battery connections.
Have you verified these same voltage readings with key on engine off, looking for observed drops in voltage, likely 1VDC or more? IE 12.5Vdc from battery to relays, key on suddenly it drops to 11.5VDC?
The PCM really REALLY hates turning on fuel pumps/injector drivers/sensors/basically everything if it sees an unsafe starting voltage. Your battery could be brand new but a tiny little bad relay or a worn out/wearing out ignotino switch not fully turning to the on position COULD put enough resistance in the wiring to drop voltage despite there seeming to be nothing wrong with battery/alternator and whatnot.

I'd say you need to take a small breath, whoo-saaah that **** for a second, and re-verify all your voltage and grounds, assuming you find janky nonsense throughout the re-verifying. Pinched wiring can look totally undamaged, but be such a high resistance connection that you look right past it.

I speak 100% from my own head bashing against hair pulling wiring issues like what it seems you are encountering. Best thing I did to help is watch SouthMainAuto'* videos on youtube. Eric O on that channel can sort ya right out. got tons of videos, might even have one for your specific video. Scanner Danner and Pine Hollow Diagnostics are also worthwhile investigating sources.

Best of luck, hope you found it by the time I get this typed up. Ill try and lend some brainstorming as much as I can, but I have a feeling a wire got pinched or something got strained and what was once communicating perfect is now visibly OK yet when measured is not passing the full signal along.