No crank no start?

No worries, I'm just glad you happened to take that picture, now we can check the BCM. I pulled all the diagrams for each connector already. So, we can check each connector with a multimeter on Monday. I need to run out for a mobile call really quick anyway, so just post back when you're home and destressed. =)

That's probably why that History code C0455 (Steering position sensor circuit malfunction) is stored in the ABS module. The actual only codes that are Current/History are the U0140(ECM lost comm to BCM), U0140(TCM lost comm to BCM), U0140(Chassis/Fuel System Control Module Lost comm with BCM),

So really the U0140 is the only active code, with these other codes are obviously an intermittent issue. Most likely a temperature or moisture related condition. We need to focus on what is happening with the BCM to begin with. When you get back, clear the codes out again and see what comes back at key On and then cranking. Considering the BCMs location and all the harness contact points that are listed in this TSB, and its where your feet are moving around down there, pressing pedals and such. I think the issue is going to be under the driver's side dash. The diagram below shows where the steering wheel position sensor is, right down where your feet will be.

Something else I find interesting is the comms code for the Fuel Pump control module is Current Diagram 2 shows that modules location under the rear of the vehicle, Near the spare tire, worst place to put a control module, but also if you look at the 3rd diagram, that's the bottom of the High Speed network diagram, there are 2 terminating 120 Ohm resistors at each end of the 2 wire high speed harness. One of the terminating resistors is inside the ECM and the other is basically strapped to the rear crossmember of the vehicle. Another terrible place to put a very important circuit component. (Diagram 3, 4)
With both terminating resistors in the 2 High speed bus, and because the 2 wires run in parallel, you can measure the entire resistance of that network from the Data Link connector and should have a 60 Ohm reading. I know that's a lot to take in at once.

But we'll first check what voltage readings we have at the BCM first and deal with anything that is missing.

Okay, enjoy the rest of your weekend.

Okay, I can't believe how many of these Chevy 5.3 and 5.7liters we're getting lately, that are all no start cases, Its one after another lately. But let me know when you want to start checking some circuits.

Okay, well, at least you already know where the BCM is located, with some codes being labelled as History codes, especially the Transfer case control module having lost comms with 4 other modules at some point, there has to be a corroded connector somewhere. What is odd is that the transfer case module comms code with the BCM is not Current, but the BCM is not setting any codes of its own. So, do another full system scan when you get a chance and see if any other codes show up. It might be that the transfer case module is offline now as well, unless some codes here are the scan tool not setting the correct Current codes, but with the key on. Clear them out and see which comes back. Modules can do very strange things when there are corroded connections. They can be ok one day, and not the next depending on outside humidity and temperature. Hopefully we can find a fault pretty quick.

That looks like an overflow hose for maybe the transmission, I'd have to look that up later.
But are the codes for the codes for the Transfer case module say "Status History" by them?
That high-speed voltage looks pretty bias, at least from there is not shorted to power or ground,
I was doing some reading up on how the BCM in your vehicle interacts with everything else and from what I read, at least part of the BCM is working because you are able to pull codes from other modules, So it might be that the BCM is lacking one or more powers and grounds, or what else I've seen with these BCMs is another module might have shorted to ground and damaged the low speed communications section, but we'll figure that out when we get into testing the BCM itself.
What I found last night was that the BCM needs to send out first an Accessory Wake Up voltage (Serial Data) for other modules to power up and this happens when the Ignition switch first hits the Accessory position, and it also needs to send out a Serial Data communications Enabled voltage. And those 2 wires are both separate from each other. So those must be happening if you're able to pull codes from a few modules on the High-speed side of the networks.
There are some testing we can do with the BCM unplugged and using a scan tool try to access certain modules. We'll try that too and see what results we get; the testing is difficult because the BCM plays such an important role in everything.

Just as a reference for you, in the diagram below shows the Acces Wake up on the dark blue wires and the Serial Data Comm Enabled is the light blue (greenish) looking highlighted wires. Granted this is an aftermarket diagram, but you can see they both originate from the Body Control module and go to different modules. So right now, you have access to the ECM, TCM, Fuel Pump control module, and Transfer case control module and there was a history code from the ABS.
Now I don't know exactly how the scan tool you're using works, apparently it doesn't show the entire network topology like higher end scan tools do. It only shows modules that are setting codes. But obviously the BCM is not fully online with other modules setting no comms with it.
I don't think you have a Trailer Brake control module, its optional on the vehicle, but with 60 ohms at the DLC, that means the terminating resistors are ok for now. I have all the wiring diagrams and connector pinouts ready for when you have time to do this testing.
2nd diagram is the BCM connectors X1-X7 and their colors.
Diagrams 3, 4 are just for you to read; it explains some network operations and power modes from the BCM and what it does during those times. Sorry I know this is a lot to take in at once, but CANBUS networks are complicated and that's what it stopping the vehicle from starting right now.

That's strange, the transfer case module was not current before. If you refresh this page, I posted some info for you to read in my last posting.

Yeah I havent looked into the transfer case module too much yet, but yes pin 10 darkBlue wire should be battery voltage. Were you reading exactly 5 volts? But I dont see any transfer case control module with that part number but Im going to run through these modules real quick, there are like 7 listed for this vehicle, I want to make to make sure the dark blue wire youre testing is not just a 5 volt reference, but in the mean time Ill post the BCM diagrams for you to check that since it will take awhile,

Now X6 and X7 didnt have any relevant pins we needed to check, but I included them anyway so you would have them, but take your time and go connector by connector. Most of these are power inputs with a couple Reference Outputs, such as a 5vRef and a 12vRef.

When you get to X3 the fun begins, thats the connector which has 2 sets on High Speed GMLAN wires, I marked them both Green for Highspeed+ and Blue for Highspeed-
but as you can see in the 23rd diagram, where its labelled "HIGH SPEED" those sets of wires are a "voltage differential" signal, thats what a CANBUS network looks like on a scope.
With a bias 2.5volts in the middle.
I put the voltage readings you should get for each, Check each of those wires with one meter lead on ground and the other on the High+ and then the High- wires.
So the High Speed Bus+ should be a 2.5v to 3.5v, the High Speed Bus- should read 2.5v to 1.5v. Its 2 signals that basically mirror each other, thats the easiest way to explain it right now. They will be a twisted pair of wires and that is to help shield them from interference.

Now pin 10 of X3 is where the BCM acts as a Gateway to the GMLAN Low speed network, I colored that is Violet. It should be a 0v to 5v signal. The 24th diagram shows all the modules on the Low Speed network, they are the ones that have that Green wire you saw when checking the comb/splice under the drivers side dash.

So that leaves us with the Lite Blue Serial Data Comm Enable signal that you already checked, I dont see an exact voltage for that yet. Ive been looking but it took me forever to do all these diagrams But I dont think its supposed to battery voltage, but I might be wrong on that.
So you can at least get started on the BCM connectors, you'll need the key On, and I dont know if you have a battery maintainer to keep a charge on the battery while doing this testing. Its always good to have one on the battery to prevent low voltage issues while testing like this. Ill verify the Transfer case module voltage you read. And get back to you, as well as the Enable voltage. But I think that if the Enable was incorrect you wouldnt be able to pull any codes at all, that again Im not a 100percent sure on.

The scan tools can communicate on different networks through the DLC. You'll have to check all these plugged in of course, when checking the Powers and Grounds, if this is possible, have a lead to Battery Negative to verify the circuit is making it all the way back to the Battery.
Sorry for the long post. Keep me updated when you get a chance. But no rush I always have plenty to do.

You are correct, the transfer case module should have the same Accessory Wake Up voltage on pin 10 dark blue X2 connector, why it only has 5 volts I'm not sure, What you can do, is with the key Off, unplug that connector, turn the key On and recheck that wire, does it still read 5v or does it jump up to Battery voltage. If it does jump up, let me know.
I don't know if you'll be able to access the ECM connector X1 without unplugging it, but I'm wondering if that Accessory voltage is the same at the ECM as at the transfer case module, because the ECM is further down the line.
These are the connectors for the ECM, X1 pin 18 is the same Dark Blue wire, if you can check it good. There is a splice that Accessory Wakeup Serial Data comes from, and we should see if the ECM is receiving that same 5volts
Even if you can pierce the ECM X1 wire to check it without having to pull everything apart, and seal it up afterwards. I put in the X2 connector here as well for reference, so you can ID the X1 easier.
I'm wondering if there is a bad splice here, or if that wakeup circuit is shorted to battery voltage somewhere.