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BMS_u029 Is the Code Killing Several Tesla Model S Battery Packs

Mario Zelaya helped us discover several unpleasant things about used Tesla Model S units. A few months after its battery pack warranty expired, his 2013 Tesla Model S Performance stopped, demanding a new battery pack to keep working. Zelaya also presented us with a new case of failure that brings our attention to BMS_u029: the error code many of Tesla’s electric sedans are showing lately to tell their owners they’re toast.
ST lost almost all the money he spent on a 2012 Tesla Model S due to the BMS_u029 error 11 photos
Photo: ST/John/Ray Johnson/edited by autoevolution
ST lost almost all the money he spent on a 2013 Tesla Model S due to the BMS_u029 errorST lost almost all the money he spent on a 2013 Tesla Model S due to the BMS_u029 errorST lost almost all the money he spent on a 2013 Tesla Model S due to the BMS_u029 errorST lost almost all the money he spent on a 2013 Tesla Model S due to the BMS_u029 errorST lost almost all the money he spent on a 2013 Tesla Model S due to the BMS_u029 errorST lost almost all the money he spent on a 2013 Tesla Model S due to the BMS_u029 errorST lost almost all the money he spent on a 2013 Tesla Model S due to the BMS_u029 errorST lost almost all the money he spent on a 2013 Tesla Model S due to the BMS_u029 errorST lost almost all the money he spent on a 2013 Tesla Model S due to the BMS_u029 errorST lost almost all the money he spent on a 2013 Tesla Model S due to the BMS_u029 error
This new case is worse than what Zelaya and Joaquim Rodrigues shared with autoevolution. This new Model S owner prefers not to tell his story with his true identity, so we’ll call him just ST (or John if you prefer). He found a 2013 Tesla Model S Performance in Toronto that would be just like Zelaya’s if it was not for the color: silver – Zelaya’s was white. On January 1, he bought it for around CAD18,000 ($13,424 at the current exchange rate). It had 207,000 kilometers (128,624 miles) on the odometer. “The back glass needed to be repaired, so the seller replaced it for CAD2,000 (1,492).”

Despite that, the car still needed more things fixed to obtain the safety certificate that would allow ST to register the vehicle in his name. He then drove it 50 km (31 mi) to the closest Tesla Service Center to check the driver-side window motor and replace rotors and pads, windshield wipers, tires, and a wheel hub. Tesla charged him CAD4,262.21 ($3,178.62) but gave him a discount, reducing the price to CAD4,001.18 ($2,983.95).

ST lost almost all the money he spent on a 2013 Tesla Model S due to the BMS_u029 error
Photo: ST/John/edited by autoevolution
The problem was what happened between leaving the car at the Tesla Service Center and picking it up:

“Beforehand, the car was charging fine, and Tesla even charged the car themselves while it was in service. No problems with the battery, and they charged it up to 90%. Tesla decided to replace the daughterboard that contains the eMMC flash card because they noticed the screen was blank. I didn’t approve this; they just did the work and updated the car’s software.”

On the surface, this situation brings up one old discussion about Tesla vehicles. If you dig a little deeper, it reveals two old problems with the EV maker.

The discussion is whether Tesla can perform updates in the car’s software without authorization from its owners. Jason Hughes, aka the Tesla Hacker, was mad at the EV maker when it forced an over-the-air (OTA) update on his Model S and removed its fast charging capability in June 2021. As a hacker, Hughes was able to make it work again but was concerned about other Tesla customers. The episode made him say that Tesla thinks it still owns the cars it sells. ST’s situation regarding software reminds me a lot of what Hughes went through.

ST lost almost all the money he spent on a 2013 Tesla Model S due to the BMS_u029 error
Photo: ST/John/edited by autoevolution
To talk about the old issues, we have to start with the eMMC flash memory card flaw. It made MCUv1 computers turn into wear parts, as the Tesla vice president of legal in charge at the time tried to argue when the National Highway Traffic Safety Administration (NHTSA) ordered Tesla to replace them in a recall. Transport Canada followed NHTSA’s lead and turned that into a recall as well, identified by the number 2021-038. In other words, it was mandatory to replace the daughterboard that contains the eMMC card that wears out, whether in the U.S. or Canada. I am not aware if it is a recall in other countries, but it should be.

That leads us to the second problem with Tesla: transparency. The Tesla Service Center that “fixed” John’s car said the component replacement was not a recall: it was “goodwill.” One that ST did not authorize, but now he knows it was compulsory. Tesla makes an abusive use of “goodwill” by classifying almost everything as such, especially items replaced under warranty.

ST lost almost all the money he spent on a 2013 Tesla Model S due to the BMS_u029 error
Photo: ST/John
Regardless of the reasons, John’s Model S was never the same.

“Immediately afterwards, the BMS_u029 error came up, and the car was handed back to me with its range limited, which forced me to sell it since I didn’t have CAD26,000 handy.”

Let me sum it up for you: ST paid CAD18,000 for his Tesla Model S, CAD4,000 to repair it, and had to sell it for CAD8,000 ($5,966), losing CAD14,000 ($10,441) in a matter of weeks. That’s almost as much as he paid for the vehicle. John feels cheated, mainly because his car was perfectly fine before the OTA update was performed, revealing the BMS_u029 error. His immediate guess was that the software update caused it.

ST lost almost all the money he spent on a 2013 Tesla Model S due to the BMS_u029 error
Photo: via TMC
According to Hughes, that is not the case. In a Tesla Motors Club Forum discussion, he explained what was happening. According to the Tesla Hacker, “the BMS only really ever resets after an update, and updates on the older cars have been pretty infrequent.” When that happens, “a lot of counters and tests are reset.”

With the MCUv1 replacements, Tesla is performing updates that are triggering tests that should be regularly performed. In other words, Hughes does not think that’s anything shady with the updates, “just crappy luck.” If it was something in the software, he swears he would have been “the first to call them out on it.” To his credit, he has done so several times in the past.

The good news is that this should stop happening when the “build date reaches about Q2 2014.” According to the Tesla hacker, that’s when “the vast majority of battery design improvements had been completed.” People with 2012 and 2013 Model S units “are pretty universally at risk of about six different types of pack failures.” From vehicles built after Q2 2014, there are “only a couple of less common ones.” Hughes said battery packs made after Q2 2015 are “super solid.” If you plan to buy a used Model S, keep that in mind.

ST lost almost all the money he spent on a 2013 Tesla Model S due to the BMS_u029 error
Photo: Ray Johnson
John disputed two main aspects of Tesla’s procedures. The first one was doing changes to his car without his permission and without properly communicating why they were necessary, such as in a recall.

“Tesla didn’t tell me explicitly about it, but I already knew about it from my research. However, when I was arguing with Tesla over the battery issue, they actually mentioned: ‘We already did goodwill by replacing the daughterboard for free.’ They didn’t mention that they have to fix it. They made it seem like it was them doing me a favor.”

ST lost almost all the money he spent on a 2013 Tesla Model S due to the BMS_u029 error
Photo: ST/John
The second relates to Tesla not offering him anything in return for the battery pack he would have to replace. The EV maker would just keep it. That was something Donald Bone also complained about when Tesla said it would have to replace the battery pack in his Model 3 for a broken coolant port nipple. The Electrified Garage fixed it for $700. ST tried to ask for help with independent shops.

“Tesla said it would be more than CAD15,000. After looking online, people have mentioned that it cost them as much as CAD24,000. I reached out to a few companies in North America: 057 Tech, Electrified Garage, and FixMyTesla out in British Columbia. The biggest barrier was the shipping, as most of them were based in the U.S., so there would be complications at customs. FixMyTesla was on the west coast, which would have been too expensive to ship.”

Even with Hughes ensuring that there is nothing shady about the OTA updates older Model S units are getting, the truth is that the tests they trigger should be performed regularly. If the goal of these evaluations is to ensure the safety of these components, there is no excuse for them to just happen with battery management system (BMS) resets.

ST lost almost all the money he spent on a 2013 Tesla Model S due to the BMS_u029 error
Photo: ST/John
On top of that, these tests are conveniently happening after several battery packs are already out of warranty. It may be a coincidence that these evaluations are triggered by an OTA update that follows the MCUv1 repair, but it is not one that owners will take lightly.

If you remember, Tesla was sued by several Model S and Model X owners after it capped the voltage in their cars. These customers accused the company of trying to hide a defect that could ignite these components. After Tesla proposed to settle – preventing any further investigation of the subject – David Rasmussen warned that the BMS_u029 was happening to several owners involved with the lawsuit. And to other people, especially those buying used Model S units.

ST lost almost all the money he spent on a 2013 Tesla Model S due to the BMS_u029 error
Photo: ST/John
Ray Johnson created a Facebook group called Tesla BMS_u029 after he purchased a 2012 Model S with 117,000 miles on the clock in October 2022. For him, the error code appeared three days after the purchase, when he was transferring the car ownership on the Tesla app. Johnson bought a new battery pack.

When I started writing this article, the group had 28 members. It now presents 35, and this article should increase that number even more. Unfortunately, this seems to be a more widespread issue than it may appear from Zelaya’s, Rodrigues’, ST’s, and Johnson’s experiences. John did not know what caused the battery pack failure in his car, but it would not surprise me if it were the water ingress that Zelaya and Rodrigues saw in their vehicles. With “six different types of pack failures” for Model S units made until 2013 and two for those produced until Q2 2015, it could be anything.
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About the author: Gustavo Henrique Ruffo
Gustavo Henrique Ruffo profile photo

Motoring writer since 1998, Gustavo wants to write relevant stories about cars and their shift to a sustainable future.
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