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I think the dealer is wrong but maybe someone will know. Generator battery control module.

R

rustyshields

New Member
Joined
Sep 21, 2022
Messages
8
Hello everyone.
New to the forum and ownership. I recently inherited my dad’s 05 Z71 Avalanche.
He was a totally disabled Vietnam Veteran. He passed away in February. I got his truck and started the work. It had been sitting for several years. I have repaired many items so far to get it starting, running and everything working.

There are two issues I am stumped on and the dealership after two visits and hundreds of dollars have done nothing but cost me more money and solved nothing.

So here goes…
They say it had a bad Generator Battery Control Module. So I purchased a genuine GM part and installed myself. I rescheduled because they said in their $700+ Estimate that it needed to be programmed. After keeping it the entire day they said it was a bad part. But I talked to the tech for a moment and he said it would not recognize. When I went back and read the first invoice that is what it said then also.

They tested power and ground and it tested ok. So my thinking is it is unlikely that I had a bad GBCM and purchased a new part that was also bad. Can’t figure out what to do next.

Thought about unplugging. Battery light stays in anyway but the issue with leaving it plugged in and not working is the 13.8 amps that make my ac, lights and other things occasionally go bonkers.

Any help will be great. Not a lot of real info on this problem online. Hoping someone can help with next steps.

Also when I got it the radio lights up and everything seems to work but no sound. Wondering if this could also have something to do with the gbcm.

Does anyone think they may be connected.
What fuses or amp should I check?

Sorry for the long post.

Thanks in Advance for any help!!
 
what was original problem?

Would not start or just check battery light or what?

Have you check all battery cables and ground straps?
Had battery load tested?
Have alternator load tested?
 
Put two batteries and three alternators thinking that the alternator was bad because only 13.8 amps. Found out when the part is bad it restricts to 13.8. So new alternator and battery. All grounds were checked and rechecked.

The funny thing is at the dealership they checked the gbcm and it had power and hood ground. They could not get it to register so they told me it was bad.

Sorry first question, yes worked to clear all lights but the battery light would not and will not clear.

Update today I tried a hard reset, drained all power with new parts still connected. After start up all the crazy symptoms were back. Mainly as I was driving around to relearn the ac was blowing flames if hell, literally like 95•.

So I came home and just unhooked the part restarted and everything working fine but of course battery light still on.
 
I guess I could have purchased a bad part and the old one was also bad. I can get another one and try it I guess. The dealership says it will have to be programmed for another 160$. Just aggravating.
 
Hello everyone.
Click to expand...
New to the forum and ownership. I recently inherited my dad’s 05 Z71 Avalanche.
He was a totally disabled Vietnam Veteran. He passed away in February. I got his truck and started the work. It had been sitting for several years. I have repaired many items so far to get it starting, running and everything working.

There are two issues I am stumped on and the dealership after two visits and hundreds of dollars have done nothing but cost me more money and solved nothing.

So here goes…
They say it had a bad Generator Battery Control Module. So I purchased a genuine GM part and installed myself. I rescheduled because they said in their $700+ Estimate that it needed to be programmed. After keeping it the entire day they said it was a bad part. But I talked to the tech for a moment and he said it would not recognize. When I went back and read the first invoice that is what it said then also.

They tested power and ground and it tested ok. So my thinking is it is unlikely that I had a bad GBCM and purchased a new part that was also bad. Can’t figure out what to do next.

Thought about unplugging. Battery light stays in anyway but the issue with leaving it plugged in and not working is the 13.8 amps that make my ac, lights and other things occasionally go bonkers.

Any help will be great. Not a lot of real info on this problem online. Hoping someone can help with next steps.

Also when I got it the radio lights up and everything seems to work but no sound. Wondering if this could also have something to do with the gbcm.

Does anyone think they may be connected.
What fuses or amp should I check?

Sorry for the long post.

Thanks in Advance for any help!!


Hi, we need more information, please start at the very beginning of what led you to the GBCM, because it seems fairly obvious it’s not the GBCM. Although, now it sounds like new part is bad, I hope you kept the old one. Was it a code? If so what was it? Also if you don’t have one get a OBD2 reader, they’re cheap. What we’re the symptoms? Do you have a phantom battery drain? This could be as simple as a lose connection at the battery terminals. Is it a new battery? I’ve solved battery issues by just replacing the bolts on a side terminal battery. Also, just a bit of advice, always carry a jumper pack powerful enough to start your truck. Replace the side bolts on side terminal batteries with extended ones that make connecting to them easier. You can also buy a disconnect switch/knob on Amazon so you can disconnect the neg side when working on your truck or if it’s going to sit for and extended time, or to temporarily solve a phantom drain problem. Although on many vehicles now being sold you never want to disconnect or replace the battery without backup power to the ECM PCM through the OBD2 port, on an 05 Avalanche that’s not a problem.

Resetting ECM
 
Short answer is the dealer. After i picked up the truck from my dads the battery light was on I replaced the battery then I replaced the alternator which had just been replaced a few months earlier I found out. Then when the alternator wouldn’t put out enough power I exchanged it for a yet another alternator. The battery light was still on after new battery and alternator. So I took it to the dealership to see if they could reprogram or clear something because it had sat for an extended period of time with no power. At the dealership they charged me $165 to tell me that it was the generator battery control module They could not get it to recognize therefore they told me it was bad. They wanted $700 to replace it. I ordered a genuine GM generator battery control module from rock auto. I installed it and The battery light was still on so I took it back to the dealership and paid another $165 for them to program that because that’s what they told me would have to be done. After leaving it there all day I went back to check on it and they said they could not get it to recognize so the new part that I bought must be bad.

I have just realized that the part that Rock auto sent me is a different part number than the original one that came out of it. I don’t know if that has anything to do with the issue or not. I have put in a warranty claim with Rock auto and I am returning the new part tomorrow they’re going to send me another one and I will try that.
 
So I hope that helps no codes ever for the battery portion just the battery light staying on in the dealership telling me that that was a bad part. It has a new battery I have a new terminals they’ve all been I’ve take them on and off multiple times they’re brand new everything‘s good and connected check those mini times check the grounds the dealership check the grounds and power to the to the module and it had power it just wouldn’t recognize so I’m assuming that it was a bad part and now I’m assuming that the part that Rocco sent me is not compatible and maybe what I need to do is try to find the actual module that came out of the truck back in 200five. I’ve been looking for those they have a different number from back then and I just can’t find any they’re all discontinued and have been sold out. It looks like the only place to find them is eBay for like 150 bucks for a used part and that’s a crapshoot. I don’t really know what to do new parts don’t seem to work and leery of old used parts
 
It is my understanding that the battery light is on because this part is restricting the output to 13.8 A. And it takes over 14 or so for the light to go off.
 
Is the module you replaced under the dash. ?
 
Summit racing has a good reputation. Is this the part you ordered? Also I wouldn’t think that the computer would need reprogrammed when replacing this part but I could be wrong. I’d try the procedure on you tube that I linked to in my previous post that uses a resistor to connect the neg and pos terminals on the truck with the battery disconnected. I would let it sit overnight to make sure all modules are drained. I’d also check the old part
Part https://www.summitracing.com/parts/ado-19432143
check this YouTube video out
it appears you can just disconnect the part with no problems
also there’s another informative post on here https://www.chevyavalanchefanclub.c...ads/05-electrical-power-management-101.42737/
 
Yes that is the part. I originally saw this video. I unhooked and drove fine until the new replacement part came from Rock auto yesterday. Put it on, disconnected battery and drained all power from modules. Same problem. Battery light is on. And some of the other stuff glows on the instrument panel as before when plugged in.
I can’t believe it is the GBCM like the dealership said it was. It just is not registering on their system. But there is no way there are three bad parts.

So don’t know what to do now. I guess work backwards. Since they say it has power and ground to the part, and I put a new part in it…I should start with a new wiring harness from the GBCM to whatever it goes to.

Any suggestions???
 
I wasn't sure part you were speaking about until watched the YouTube post.
On my 07 it's similar part but called negative battery cable sensor. On my model I replaced it without programming anything.
The power control module and body control module both need pre/programming & additional programming after installation. If have the tech2 programming software/tool can probably not buy already programmed.

I spent 28$ at auto parts store to get Haynes repair manual. They have good detailed wire diagrams in back can probably help you, it didn't have everything I was looking for my 07 but did help me fix many electrical problems.
 
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