I just got back in the vehicle and tried to rescan the modules and I have 0v at the obd connector and no module will respond. This car has a very strange electrical gremlin, should I start calling LKQ now? lol!

 

Check the fuses

https://fuse-box.info/chevrolet/chev...uses-and-relay

I believe it’s fuse #29 for the obdII port

 

Fuse is good. I checked back 30 minutes later and power is back. I may need to trace the power cable from the battery to the fusebox. It's odd how it provides full voltage to the fusebox and then when this power problem happens theres 0 voltage all the way across.

 

is not good enough!!!!!!!!
All of those connections between the halves must click in.
​​​​​​​Your description sounds a lot like the run/crank relay #51 has some sort of problem.
Replace anything you want to like a dealership mechanic would. Heck, it must be a computer

The only connection between the driver door and the power system is the Retained Accessory Power system and the interior dome lights. Opening then closing the driver door turns RAP off, RAP goes to the windows and door locks. Maybe look for shorts in the interior lights system. The dome lights are controlled by the BCM, the door switches/sensors send a signal.

A little history would probably help.

FREE Shop Manuals via the link in my sig. If that is too difficult here is the url: charm.li

 

Tighten the bolt in the BCM

 

Relay #51 is getting power and is clicking, I swapped with another relay and still the same issue. When the ignition is on I can hit the starter relay to make the vehicle start but it only runs for 2-3 seconds until it runs out of fumes I assume. I added a few gallons of fuel just to make sure it isn't empty because the fuel gauge reads zero but no luck.

 

[QUOTE=Oldblue;956730]Tighten the bolt in the BCM[/QUOTEI]
I'm starting to think maybe the BCM is toast. All the ECM/TCM fuses are getting power and relays are clicking, maybe the BCM or signal? Not sure. I have a used BCM to throw in but I would need to program to the vin on these models, right?

 

You’re thinking way to much, try focusing on our suggestions, tighten the bolt and try to start.
if you did in fact disassemble the fuse box the remove the engine for the timing chain replacement, double check the ground wires, tighten the starter wires, the alternator wire.

 

[QUOTE=LaskoHHR;956789]You start replacing modules you will not like the results. Over 90% of BCM's replaced are fine. PCM's over half. You need to be sure the network is good and that you have good power and grounds to the module before condemning it.

 

The studs on the side of the underhood fuse block, 2 large (red or black)wires to the front, 1 small (red) wire to the back.