No Start/Crank after write - U0140 BCM Comm Loss - 2007 Sierra NNBS 4.8l

First time fiddling with HP tuners, was going to install some gears and a posi this weekend and wanted to get a feel for flashing, etc. 2007 4.8l 4l80e new body style sierra. Pulled my stock file a few months back, just updated it today with a new tire size and wrote the config. Write was successful but I have no start/crank. No power windows or radio turning on. I wrote back the original config file and it was successful, still same result. When I scan the truck and pull codes all I see is U0140 loss of comm with body control module (pending). I'm hoping nothing is fried as I can still flash/connect to the ECM/TCM.

I did some reading and saw some recommend pulling the negative battery terminal and waiting for some time but any other insight would be helpful. Tunes are attached but not too much to them.

Some additional details from the last few hours:

- I can read the ECM/TCM without issue.
- The cluster does not react when writing, (thought you would see some movement here/there)
- Had negative terminal off for an hour, no change.
- Checked BCM fuse, no issue.
- Removed and re-plugged all BCM connections. No change.
- Voltage at battery is 12.18 so don't think there would be any issue here.
- No indicator line under PRND321 in the gauge cluster.
- Oil pressure and Fuel level gauge show 0/empty with key on.
- Service Airbag displayed on DIC after write.

I found this thread;

https://forum.hptuners.com/showthrea...ight=fried+bcm

Noticed the last post referring to the BCM just going bad and after being forced to lose communication during the flash it wont come back. Anyone have any other suggestions before I go replacing the BCM?

not sure with yours but is there a fuse for the comms ? mine has one i popped one time unrelated to tuning so just a thought

Quote:

---

Originally Posted by 07GTS

not sure with yours but is there a fuse for the comms ? mine has one i popped one time unrelated to tuning so just a thought

---

I poked around inside and was only able to find a 10amp fuse specifically for the BCM but I'll take another look in the morning. I left the negative terminal off for the night so I'll see if that helps at all. Truck was fine and was running no more than 5 minutes before writing and having these comm issues.

As far as I can tell I can read/write/scan the ECM/TCM so I hope its something stupid I'm just missing.

Some more detail from this morning;

- Negative batt cable disconnected overnight, didn't help.
- Checked every fuse that had something to do with the BCM, no issues.
- I can hear the fuel pump prime with the key on.
- Only lights that stay lit after key has been on are ABS and check engine, still no line under gear selector indicator.

I've got it on the charger now but pretty much out of ideas other than bad BCM.

Try to write entire with the original tune you pulled.

Quote:

---

Originally Posted by PGA2B

Try to write entire with the original tune you pulled.

---

Entire write with the original tune was successful just now but same results. No comm with the BCM.

Did you clear the code before you did the write entire or did the pending code not show a CEL?

Unfortunately, it sounds like the BCM is bricked. I've had that happen to me as well. You'll likely have to replace it.

There was an earlier version of HP Tuners that had a problem with this. They issued a critical update for it. What version are you using?

Quote:

---

Originally Posted by PGA2B

Did you clear the code before you did the write entire or did the pending code not show a CEL?

---

I've cleared it a handful of times but it comes back every key cycle. Can't say I cleared it right before the full write.

Quote:

---

Originally Posted by kevin87turbot

Unfortunately, it sounds like the BCM is bricked. I've had that happen to me as well. You'll likely have to replace it.

There was an earlier version of HP Tuners that had a problem with this. They issued a critical update for it. What version are you using?

---

Interesting, I'm using the latest version 4.4.4. I've searched around for the better part of the last two days and have only seen one other mention of this. Is there any rhyme or reason to why it bricked or just an unlucky roll of the dice?

In all likelihood, It was just an unlucky roll.

Wanted to follow up with a resolution, BCM was cooked. Plugged in a newly programmed one and the truck fired right up. Haven't tried to flash again yet but BCM was it.

Nice to hear that you fixed your problem. Can you help me please. I got a 2009 nnbs with an 4l80e. I ordered a ICT harnees only to find out that it is for the NBS. How can I wire the speed sensor wires to the ecm. Mines has 2 connectors grey and black.