GM Volt Forum banner

BECM Refurbishing/Repair Offer

14K views 50 replies 25 participants last post by  DerBassSpieler 
#1 ·
I have been doing component-level electronic repairs for the past 50 years. I have an educated hunch at which type of component(s) are going bad in the BECM. I would love to get my hands on one to see if I could repair it. If I can fix one, I could probably fix nearly all of them.
 
#2 ·
From another thread:

If anyone has a BECM that has failed and wants it repaired, please let me know and we can arrange to have it sent to me for inspection. If it cannot be repaired I will return it in the same condition at my expense. If it can be repaired, I will do the first one at no charge.
For those with long wait times on replacement BECM's this could be of interest.
 
#3 ·
It would be interesting to crack open of those BECM modules open and see if there is any obvious burned components. I've wondered why the Gen 2 is having so many go bad. Most of the modules I've seen for the Volts have MADE IN JAPAN stickers on them. That use to be a bad thing, now as we all know Japan is one of the leaders in manufacturing design and quality. Especially automotive and electronics. Being located on top of the battery could possibly getting hotter than the engineers thought it would? If you could narrow down the component level culprit it would most likely be a surface mount part. Not a problem to replace with the right soldering tools/bench. If it is a surface mount IC issue, I've found a lot of those are proprietary chips designed specifically for that module. So you might run into the same issue the manufacture is having getting the chips. But definitely worth opening one up and taking a look.
 
#5 ·
I agree... I suspect fractured solder joints more than failed ICs. It's often the case that a PCB will have inadequate pad space for the soldered joint to a higher amperage component and over time, it fractures due to heat. In addition, manufacturers have moved to more eco-friendly solders which can be more subject to this. So it will indeed be interesting to do a deep dive on a failed BECM to determine the real failure mode.
 
#7 ·
One guy tried to repair the BECM. He discribes, that he eventually had to disassemble the car 11 times before he decided to buy a new one. It was some time ago.

He says they tried resoldering components. It seemed everything started to work, but after a day or two of driving it started failing again. Then they tried to freeze the module in the fridge after resoldering and it caused it to fail.

After some time he said they managed to repair, but again after a couple of months he decided to install a new one.

So, not knowing the real cause I think it's almost impossible to repair it, especially without bench testing and road testing.
 
#10 ·
It would seem to be an exercise in futility trying to "fix" the module without the factory test fixture with diagnostic CAN bus software. It would be useful to have it running balance routines and temp ranges with a program/environment that puts the module through the paces of the lookup tables. Conformal coating is also a bitch to work with...no thanks.
 
#11 ·
Ambitious project for sure, if someone can find a fix for these a lot of Gen 2 owners would be more than grateful. Especially in the next few years as the 8 year warranty expires to fix these for free. The first hurdle, getting your hands on a bad one will be difficult. The only folks that will have access to one will be the dealerships that are replacing them under warranty. Need one of the Volt techs out there to send one to you instead of tossing it in the dumpster or in the bottom or their tool box with the other bad modules. I would think if someone with a garage and lift could successfully repair problems like this and replacing battery sections or even cell packs they could do very well. Especially if gas prices remain where they are now. A Volt that became a lawn ornament is now highly sought after.
 
#17 ·
where are you located? I'm in MD and while my BECM is still good for now, GM probably won't warranty mine if it goes bad due to my salvage history. PLan A would be to jerry rig it to always be on. PLan be would be to buy a wrecked one with the vin history showing becm replaced and swap it over.. or one with a dead battery..
 
#21 ·
I still call them Lucky Goldstar.

IR surface mount soldering with the new solder can result in heat/cool/vibration failures however the process when implemented properly through the whole cycle is very reliable. When you look at all of the devices out in the field the failure rate for IR soldering is pretty low. Component lead oxidation can be a problem where the chip connections do not wet properly and flow with the circuit board pads. The qual on components for automotive in many cases is higher than satellites so it would be unlikely to see boards built by highly reputable companies using oxidized or low spec components.

Small Chinese job shops that dump many clones on Ebay often use "floor sweepings" or old surplus components...whatever they can source cheap to build their devices. Those often have a higher failure mode however you get what you pay for...many times a pretty good deal.



Most of the problems I see are heat related with boost and buck power supply caps being the main things to fail. We can speculate until the cows come home about the failure mode of the BECM. Hopefully someone in the know will leak out the failure mode.
 
#24 ·
want my guess
the through holes are to small and crack inside the board
why do i say that
core charge, gm wants them back
Circuit board vias that link multi-layer boards are a known failure mode when not implemented right so your speculation is quite plausible.

In the old days we would suck out the solder...insert a wire and solder the top and bottom sides of the board to fix. The problems often were intermittent and would test continuity top to bottom on the bench only to open under heat and or vibration (18 wheeler). I helped a buddy back in the late 70s repair and mod trucker CBs and amps at his shop and we saw many failures related to that.

I detest surface mount repair although I do it when necessary to save money and/or take care of a problem quickly. The vias these days are a lot smaller and the boards are often more than 2 layers. Most of my ham equipment is tube or through hole so it is easy to maintain. I repair what broadcast equipment I can however the manufactures these days hold their documentation close to the vest so the IR camera test and obvious bulging caps are about as far as I go. Oh, and I'm an old fa**.
 
#30 ·
The vias these days are a lot smaller and the boards are often more than 2 layers.
That's an understatement. I would be surprised if the board is less than 8 layers. Traces will be 3.5 mils or smaller getting in and out of the BGAs. All while dealing with high voltage compatibility in other places on the PCB. Not an easy task to get the solder profile correct for fine pitch BGAs and high voltage at the same time.

LG made the battery cells/modules for GM, so it makes full sense that they would supply the BMS at the same time. Who else would know the battery chemistry better than the company that made the cells?

-Charlie
 
#29 ·
Not the whole car, just the BECM related things. A B2B warranty for a bumper defect is not going to be affected by installing my own shifter micro switch for example.
 
#31 ·
8 or more layers - that's almost irrelevant, as there're always no more than two layers, which have components: the top and the bottom. The purpose of all of those tiny lines and vias is to connect that components. Thus, any faulty line or via could be dubbed with tiny wires if one knows where's the fault.

The exceptions are the lines designed to carry some high frequency data - dubbing those lines could cause rf-interference due to extra inductance/capacitance/resistance of external wires.

The fact that all BECMs have similar failure symptoms (lost communication with battery modules 7-12) suggests the fault is with some higher-level chip. Maybe the comm or VCC line of some chip is broken. Connection with an external wire could help.

If I ever manage to buy a new design board, I will make high-res pictures of the old and new boards to be able to compare the design and components. Maybe there'd be something interesting.
 
#32 ·
Due to all the chatter about failed BECMs, GM's Technical Service Bulletin 18-NA-261 document has probably been attached somewhere in another post. That said, here it is. I was surprised to see the March 9, 2022 "Version 2" update that specifically references the new PN 24296900, and added the 2019 model year. The original version from 2018 referenced the old faulty PN.

My 2018 Volt is at the dealer for this issue right now. I assumed the service department would have quick access to these documents, but they seemed to be searching for it as of our last call. Makes me wonder if the updated version will also come to their attention. It should, but at the moment, I seem to know as much as they do about this particular problem. Share this document for others who need to know!
 

Attachments

#35 ·
when i use to fix boards, every component was big and you could fix it, today with surface mount components, i just change boards. could be as stupid as the ic or chips are small and overly warm.
I stopped fixing them when i found out that the heat from the chip was heating the board under it and the trace failures were happening under the chip
replacement boards would have the ic sitting higher off the board, go figure
not saying this is gm problem, but u get the idea
 
Top