I suspect BCM... thoughts?

[sunureu13]

Ooh, we've got new info. I'm pulling U0101 and U0102 codes (lost communication with TCM and Transfer case). Well that would explain the dash errors.

Looks like I've got some deeper inspections to do. I found a longer/more detailed TSB document here: https://static.nhtsa.gov/odi/tsbs/2012/SB-10043829-6448.pdf

So the short version is, every single harness everywhere in the vehicle could have been rubbed through somewhere and everywhere all at once. Yay me.

Anybody want a 2500 suburban? Ugh.

I wrote a big long post while you were posting this. But here's the relevant wiring diagram about what could cause the lost comm with tcm and tc. Those are passed through the bcm.

Again, it could be the bcm getting a bad ground. I'm fairly certain the direct ground for the bcm is on the outside of the frame on the driver's side under the front door, near the cab mount. Small ring terminal. Can get pretty nasty under there especially in snowy places or with fleet vehicles. That ground goes into the harness near it (you'll see it) and I believe that goes up to the junction box. I still need to find my diagrams. I know alldata has them but my subscription lapsed. Might have to resubscribe.

 

[petethepug]

Again, I’ve seen this in another early 07 just a month or two ago. The owner, with close to three decades turning wrenches in the Army, nailed it with the BCM.

There GM Document ID# 2009971 stating the BCM/RAP should have a module reflash.
The cost, $129 for a coded replacement BCM, is much less vs a reflash.

This was the main reason the 07 Esky owner went this route. He just took the same truck from GA to FL last mo on a family vacation.

Reliable Automotive Electronics Rebuilder | ARES Technologies

An automotive electronics rebuilding leader, ARES Technologies delivers high-quality ECM, PCM, TCM, and FICM modules for vehicles. Shop online!

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Keep in mind the BCM controls the smart charging feature of the battery.

This is another interesting clip to follow…

 

[TrybalRage]

I wrote a big long post while you were posting this. But here's the relevant wiring diagram about what could cause the lost comm with tcm and tc. Those are passed through the bcm.

Again, it could be the bcm getting a bad ground. I'm fairly certain the direct ground for the bcm is on the outside of the frame on the driver's side under the front door, near the cab mount. Small ring terminal. Can get pretty nasty under there especially in snowy places or with fleet vehicles. That ground goes into the harness near it (you'll see it) and I believe that goes up to the junction box. I still need to find my diagrams. I know alldata has them but my subscription lapsed. Might have to resubscribe.

I've already wirebrushed that ground connector with no change, unfortunately.

 

[Fless]

Again, I’ve seen this in another early 07 just a month or two ago. The owner, with close to three decades turning wrenches in the Army, nailed it with the BCM.

There GM Document ID# 2009971 stating the BCM/RAP should have a module reflash.
The cost, $129 for a coded replacement BCM, is much less vs a reflash.

This was the main reason the 07 Esky owner went this route. He just took the same truck from GA to FL last mo on a family vacation.

Reliable Automotive Electronics Rebuilder | ARES Technologies

An automotive electronics rebuilding leader, ARES Technologies delivers high-quality ECM, PCM, TCM, and FICM modules for vehicles. Shop online!

arestechnologies.com

Keep in mind the BCM controls the smart charging feature of the battery.

This is another interesting clip to follow…

The link seems to be for ECM/PCM modules.

 

[TrybalRage]

Keep in mind the BCM controls the smart charging feature of the battery.

This is another interesting clip to follow…

Yep, that video is pretty much what I'm experiencing. Although today, the error just says 4WD, at other times it will say traction/airbag/etc/etc/etc.

 

[sunureu13]

The link seems to be for ECM/PCM modules.

That's just the preview for the link. Pete posted the link to the main site, gotta put in your relevant vehicle information.

 

[sunureu13]

I've already wirebrushed that ground connector with no change, unfortunately.

That's good (and bad).
I went through the troubleshooting in the TSB you linked and it didn't take too long to check for chafed harnesses, bad resistor, loose connectors, etc. Maybe a little more than an hour.

I also reseated all the connectors on the front side of the BCM as well. Once my battery is done charging I will see what happens when I disconnect the bcm or suspension module like in the video. If that "fixes" it, I'm still not 100% sure that means the module is bad or if that could still be a ground issue.
If you want to disconnect the suspension module, I think you have to unbolt it from the frame. At least on my truck (07) the evap canister lines and harness is in the way of the connector.

 

[Rocket Man]

That's just the preview for the link. Pete posted the link to the main site, gotta put in your relevant vehicle information.

Go ahead and try, they don’t list anything for the OP’s vehicle. And they don’t do BCM’s according to that website.

 

[TrybalRage]

That's good (and bad).
I went through the troubleshooting in the TSB you linked and it didn't take too long to check for chafed harnesses, bad resistor, loose connectors, etc. Maybe a little more than an hour.

I also reseated all the connectors on the front side of the BCM as well. Once my battery is done charging I will see what happens when I disconnect the bcm or suspension module like in the video. If that "fixes" it, I'm still not 100% sure that means the module is bad or if that could still be a ground issue.
If you want to disconnect the suspension module, I think you have to unbolt it from the frame. At least on my truck (07) the evap canister lines and harness is in the way of the connector.

I'm fairly certain I don't have a suspension module as I have a 2500 with truck-style leaf springs and traditional shocks. I can still take a look though.

I've already removed and reseated the bcm connectors. I'm also going to clean and check the PCM connectors as well. I've already looked at the transmission connector but did not spend a lot of time inspecting the harness there.

 

[sunureu13]

I'm fairly certain I don't have a suspension module as I have a 2500 with truck-style leaf springs and traditional shocks. I can still take a look though.

I've already removed and reseated the bcm connectors. I'm also going to clean and check the PCM connectors as well. I've already looked at the transmission connector but did not spend a lot of time inspecting the harness there.

You won't have the suspension module, that's only for autoride-equipped models.

I've been through basically everything I could check and it's still pointing towards bad BCM. Pulled all the modules one at a time, checked resistance on pisn 6 & 14 of the obd2 port (should be about 60ohms). Poked around on the BCM connectors to see if there's power (there is). I can communicate with every module except bcm and bcm is still the only relevant dtc I have (checked with tech 2).
I've done basically everything short of checking the wiring diagram and putting probes on each side of every circuit.
Another thing I noticed is that I have low speed bus communication with stuff the BCM controls (windows, locks, hvac, etc) but no high speed bus communication (most notably interior and exterior lights). I still don't exactly know what that means but I'm going from there.

Here's another great resource for this issue:

Schematics, Pinoouts, Training Materials, Technical Documents - PerformanceTrucks.net Forums

Tuning, Diagnostics, Electronics, and Wiring - Schematics, Pinoouts, Training Materials, Technical Documents - We can get GM technical documents if you need then.

www.performancetrucks.net

 

[sunureu13]

Ended up resubscribing to alldata for a month. $20 for a single vin isn't terrible. Didn't have much in terms of diagnosis but the wiring diagrams helped a lot.
I still wasn't able to definitively say that the bcm is the culprit, but I did rule out plenty of other things. I was getting voltage to the bcm, the high speed bus wires were not shorted (the ones for pins 6 & 14 on the obd2 connector, mine were tan and tan/blk, twisted pair, can't miss it) at the bcm. Resistance at the two wires were the same. I checked that the "output" wires were getting voltage.
Other than that I can't think of any other things I can check. I'm gonna go ahead and order a preprogrammed bcm because to do it myself would cost me about the same.

 

[Rocket Man]

Ended up resubscribing to alldata for a month. $20 for a single vin isn't terrible. Didn't have much in terms of diagnosis but the wiring diagrams helped a lot.
I still wasn't able to definitively say that the bcm is the culprit, but I did rule out plenty of other things. I was getting voltage to the bcm, the high speed bus wires were not shorted (the ones for pins 6 & 14 on the obd2 connector, mine were tan and tan/blk, twisted pair, can't miss it) at the bcm. Resistance at the two wires were the same. I checked that the "output" wires were getting voltage.
Other than that I can't think of any other things I can check. I'm gonna go ahead and order a preprogrammed bcm because to do it myself would cost me about the same.

Fingers crossed.

 

[TrybalRage]

Ended up resubscribing to alldata for a month. $20 for a single vin isn't terrible. Didn't have much in terms of diagnosis but the wiring diagrams helped a lot.
I still wasn't able to definitively say that the bcm is the culprit, but I did rule out plenty of other things. I was getting voltage to the bcm, the high speed bus wires were not shorted (the ones for pins 6 & 14 on the obd2 connector, mine were tan and tan/blk, twisted pair, can't miss it) at the bcm. Resistance at the two wires were the same. I checked that the "output" wires were getting voltage.
Other than that I can't think of any other things I can check. I'm gonna go ahead and order a preprogrammed bcm because to do it myself would cost me about the same.

I did the same today. So good luck to us both, I guess. I haven't dug in nearly as deep as you have, I'm just hoping it works.

 

[TrybalRage]

New BCM arrived yesterday. Put it in and it fired right up, did not give me a security/key relearn issue. However I am getting an airbag error, which according to the paperwork still needs to be cleared by a scan tool. Blah. So I guess I'll have to take it to a shop... I don't think I need a dealer Tech2 tool, from videos it looks like other scan tools (like SnapOn) can do it as well.
I guess now we wait again to see if the no-crank issue pops up again. Gonna be a hot day so it'll be a good test.

 

[swathdiver]

New BCM arrived yesterday. Put it in and it fired right up, did not give me a security/key relearn issue. However I am getting an airbag error, which according to the paperwork still needs to be cleared by a scan tool. Blah. So I guess I'll have to take it to a shop... I don't think I need a dealer Tech2 tool, from videos it looks like other scan tools (like SnapOn) can do it as well.
I guess now we wait again to see if the no-crank issue pops up again. Gonna be a hot day so it'll be a good test.

In Florida by chance? Check the Tech-2 owner's thread to see who is close to you.

 

[TrybalRage]

Nope, eastern PA. The Tech-2 owners thread shows someone about an hour from me.

 

[petethepug]

Well played. The previous owner was likely occasionally dealing with it too. Enjoy your 39 gal tank when you find cheap fuel. The rest of us are stuck with 26 as max cap.

 

[TrybalRage]

Day 2 of sitting in the hot sun with no issues. Fingers crossed, feeling cautiously optimistic. I hate having a vehicle I can't trust.

 

[sunureu13]

Day 2 of sitting in the hot sun with no issues. Fingers crossed, feeling cautiously optimistic. I hate having a vehicle I can't trust.

Good to hear. Still going strong?
I'm still waiting for my bcm. A week latr despite the fact that I opted for the 2-day air from work.

 

[TrybalRage]

Good to hear. Still going strong?
I'm still waiting for my bcm. A week latr despite the fact that I opted for the 2-day air from work.

So far so good. I still haven't had the Airbag reset yet, I do need to make an appt for the recall so I might as well kill two birds with one stone on that one.

I ordered mine from the ebay link someone shared earlier in the thread. They got it to me fairly quickly.