UI_a112 - USB device malfunction - I/O Error

[BitJam]

Yup, fresh out of the factory on Tesla's latest and greatest and the UI_a112 notifications started spewing out. I have scheduled a SC appointment just so I can get this issue logged in their books but based on what everyone has said there's no point in 1) swapping flash drive 2) changing the USB hub 3) changing the MCU. Will just have to wait for the SW fix.

Replacing the computer worked for at least one person:

My USB-A wasn't recognized, and the format and delete options were grayed out. I tested the USB on my computer, it worked perfectly fine. Tesla verified that there was an issue and replaced the computer (1684435-S0-1). Works fine now and sentry is working.

I've mentioned before that Tesla almost certainly uses different usb controller chips in different vehicles and even in the same vehicle. Each controller chip can use a different software driver. If one of the drivers is bad the problem can affect some cars and not others. I'm one of the people who has a consistently working glovebox usb port but a non-working center console usb port.

It seems at least possible that the service center will be able to fix the problem for you by swapping hardware.

 

[Mike_TV]

I've mentioned before that Tesla almost certainly uses different usb controller chips in different vehicles and even in the same vehicle.

During the supply chain issues in 2021-22 they said one of the things that Tesla delivering cars was being able to write firmware, on the fly, from different chipsets and vendors that had then in stock. Something like 26 different chip designs for the same purpose.

 

[Tha_Ape]

I have only seen the error on my 2021, and only with the center USB-Cs.

No issues with the glovebox one in either of my cars

 

[ElectricAnt54]

I believe have seen people with older model 3 which lack glovebox usb port (so they claim) have the issue in their center console usb-a ports. Basically they have no way to have functional dashcam feature & sentry mode…nor usb music.

Personally my 2022 model y with Tesla OEM usb-c module which supports data has the issue since 2/2024 & my glovebox usb-a works fine.

 

[BitJam]

During the supply chain issues in 2021-22 they said one of the things that Tesla delivering cars was being able to write firmware, on the fly, from different chipsets and vendors that had then in stock. Something like 26 different chip designs for the same purpose.

Good point but I think this is something different. Tesla would write code for micro-controllers which I'm sure abound in the car. But they probably wouldn't write low level code to interact with a usb controller. That is usually done with a driver in the Linux kernel. The kernel uses the pci id of the controller to know which driver to load so, as long as nothing goes wrong, changing usb controllers is transparent to the Tesla devs.

I'm sure Tesla periodically updates their Linux kernel as part of some firmware updates. If a bad driver got into one of the updates then it would explain much of what we are seeing. The problem would start after a Tesla firmware update. Some usb ports on some cars would have the problem. Other ports on other cars could be okay. A hardware swap might fix the problem for some people.

A bug in a driver that is part of the Linux kernel would also explain why this problem hasn't been fixed quickly. AFAIK, Tesla engineers are not working on the Linux kernel. For a minor problem** like this, Tesla would wait for the fix to get into the next stable kernel instead of patching their kernel to add only this fix. In addition, a Tesla firmware release with a new kernel will need to go through more testing than a normal point release would require.

You can find out more about how a computer interacts with usb controllers here: Extensible Host Controller Interface. The Linux driver for this is called xhci-hcd. Over the years there have been several similar problems with this driver where people lose connection with their usb devices and need to reboot to fix it.

** Lives are not at stake nor is FSD or Autopilot.

 

[Flybyglass]

I believe have seen people with older model 3 which lack glovebox usb port (so they claim) have the issue in their center console usb-a ports. Basically they have no way to have functional dashcam feature & sentry mode…nor usb music.

Personally my 2022 model y with Tesla OEM usb-c module which supports data has the issue since 2/2024 & my glovebox usb-a works fine.

I have a 2020 Model 3 with the center console dual USB-A ports and no glove box port. The USB A's work and dash cam works but I get transitory UI_a112 like many others and have done the drive change to from 256GB to 128GB with same results. It happens at odd hours when car should be asleep like a data pull from Tesla but even some have selected no data sharing and they still see it. It doesn't generate any messages min service mode and no messages are active only past and don't appear to be interfering with anything. Since this is happening across all model years it must be software.

 

[ucby]

Good point but I think this is something different. Tesla would write code for micro-controllers which I'm sure abound in the car. But they probably wouldn't write low level code to interact with a usb controller. That is usually done with a driver in the Linux kernel. The kernel uses the pci id of the controller to know which driver to load so, as long as nothing goes wrong, changing usb controllers is transparent to the Tesla devs.

I'm sure Tesla periodically updates their Linux kernel as part of some firmware updates. If a bad driver got into one of the updates then it would explain much of what we are seeing. The problem would start after a Tesla firmware update. Some usb ports on some cars would have the problem. Other ports on other cars could be okay. A hardware swap might fix the problem for some people.

A bug in a driver that is part of the Linux kernel would also explain why this problem hasn't been fixed quickly. AFAIK, Tesla engineers are not working on the Linux kernel. For a minor problem** like this, Tesla would wait for the fix to get into the next stable kernel instead of patching their kernel to add only this fix. In addition, a Tesla firmware release with a new kernel will need to go through more testing than a normal point release would require.

You can find out more about how a computer interacts with usb controllers here: Extensible Host Controller Interface. The Linux driver for this is called xhci-hcd. Over the years there have been several similar problems with this driver where people lose connection with their usb devices and need to reboot to fix it.

** Lives are not at stake nor is FSD or Autopilot.

This explanation seems plausible. I agree that there will be multiple sources for USB controllers as all large companies will use multiple vendors to limit supply risk and improve pricing. This might explain why an MCU swap could fix a firmware issue as the change may swap in a USB controller from a different vendor that doesn't have the compatibility issue.

BTW, when I look closely at the UI_a112 errors report on the web I think people might have different issues that are all grouped under the same error. Some people report that once they see the error the USB drive is no longer mounted and requires a reboot / reformat / unplug and plug / etc. I don't see that. Me USB drive stays mounted and Dashcam is recording ok. The only issue I see is the error in my notification at random times. I'm guessing the drive may be unmounted but gets remounted automatically.

 

[legendsk]

But more importantly, does the Screaming Goat noise still work with 2024.14.9? Mine shows a pending update waiting and I'm afraid to install it. I would hate having to go back to hauling a passenger in order to have the screaming goat noise, when the car does scary stuff.

 

[⚡️Mr. JARE_EE]

I am experiencing same issue 2020 MY with center console usb. It is happening every morning in deep sleep. I am trying to see if it is because of the schedule departure in the morning. My USB is the Samsung Bar Plus. At first i thought it was my SD card so i changed to USB. Currently on 2024.14.9.

 

[Flybyglass]

It appears Tesla MAY be working the UI_a112 issue. Previously, the message showed up in transitory messages with no current warning (at least on my 2020 M3 with noting in service mode notifications. Now in service mode customer alerts it shows up with additional information including that the car may reboot to solve the problem. Tesla is data driven on things and while it's not a fix, they seem to be adding self correcting (think auto reboot if message occurs). I would expect with the volume of this messages across the fleets that should now be picked up during data sweeps, they are finally focusing.

 

[⚡️Mr. JARE_EE]

2024.20.1 - still not fixed.

 

[BitJam]

It appears Tesla MAY be working the UI_a112 issue. Previously, the message showed up in transitory messages with no current warning (at least on my 2020 M3 with noting in service mode notifications. Now in service mode customer alerts it shows up with additional information including that the car may reboot to solve the problem. Tesla is data driven on things and while it's not a fix, they seem to be adding self correcting (think auto reboot if message occurs). I would expect with the volume of this messages across the fleets that should now be picked up during data sweeps, they are finally focusing.


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Thanks for the info!

This is bizarre. Automatically rebooting a system to get a usb port to work is an ugly kludge in the Linux world. I started doing Linux sysadmin over 25 years ago and I don't think I've ever seen anything quite this ugly in that entire span.

But one thing that does not support this theory is I haven't seen recent Linux bug reports about this issue. There were reports in years past, often associated with the autosuspend feature, of usb devices disconnecting and requiring a reboot to fix.

 

[BitJam]

Possible solution/work-around. I've only tested this once and I had the windows vented which might have caused the computer to stay on and keep the usb working.

The Linux problems with usb autoresume and the fact that some of us have a working glovebox usb but a failing center console usb made me think that perhaps it's only the higher speed, higher power usb-3 devices that are failing. So I put my music onto a low power sdcard.

The sdcard usb device was available when I unlocked the car automatically with my phone key. Again, this might have been because the windows were vented.

 

[ucby]

Possible solution/work-around. I've only tested this once and I had the windows vented which might have caused the computer to stay on and keep the usb working.

The Linux problems with usb autoresume and the fact that some of us have a working glovebox usb but a failing center console usb made me think that perhaps it's only the higher speed, higher power usb-3 devices that are failing. So I put my music onto a low power sdcard.

The sdcard usb device was available when I unlocked the car automatically with my phone key. Again, this might have been because the windows were vented.

It's possible. I swapped out my Tesla provided USB stick for a 2TB Samsung T7 SSD. It's been running for about a week so far with no error messages. Used to be more frequent before. Doesn't mean it's a solution as others have reported intermittent stability with swapping drives but just wanted to add another data point.

 

[⚡️Mr. JARE_EE]

It's possible. I swapped out my Tesla provided USB stick for a 2TB Samsung T7 SSD. It's been running for about a week so far with no error messages. Used to be more frequent before. Doesn't mean it's a solution as others have reported intermittent stability with swapping drives but just wanted to add another data point.

Are you not getting any errors in the notification? That's pretty good. I might consider trying a SSD option but it's quite expensive.

 

[BitJam]

It's possible. I swapped out my Tesla provided USB stick for a 2TB Samsung T7 SSD. It's been running for about a week so far with no error messages. Used to be more frequent before. Doesn't mean it's a solution as others have reported intermittent stability with swapping drives but just wanted to add another data point.

A 2TB Samsung T7 SSD is not slow or low power. My theory was that a slower device that drew less power might be a temporary solution. But if you found something that works, that's excellent!

I tried it again just now after the windows had been closed for hours. The music sd card in the center console was still accessible from the car's screen after my phone key automatically unlocked the car.

I use this reader/adapter (you need to order an sd card with it). AFAIK, the Samsung PRO Endurance has the best environmental and endurance specs but the one that comes with the read/adapter should be fine and should be much better than all or almost all usb drives and ssds.

If the lack of usb access is a problem for anyone, then I recommend trying an sd card with adapter. This is what I've been using for a while in my glovebox for TeslaCam after my Samsung T5 ssd died prematurely. There have been many posts here about the superiority of a good sd card for the TeslaCam device so I won't repeat them here. Throughout this ordeal I've had problems with normal usb flash drive in the center console for my music but the sd card in my glovebox has always worked just fine.

Others have reported their glovebox device worked but the music device in the center console failed. I thought that perhaps they too may be using an sd card in the glovebox.

 

[ucby]

Are you not getting any errors in the notification? That's pretty good. I might consider trying a SSD option but it's quite expensive.

Correct. Zero user notifications and nothing in the service menu either. I've briefly checked over the recorded footage looking for breaks in the video but it looks clean so far. I'll report back if anything pops up. BTW, if you're going to try an SSD my T7 could format to exFAT in the car but I had to create the "TeslaCam" and "TeslaTrackMode" top level directories with my computer.

 

[Flybyglass]

A 2TB Samsung T7 SSD is not slow or low power. My theory was that a slower device that drew less power might be a temporary solution. But if you found something that works, that's excellent!

I tried it again just now after the windows had been closed for hours. The music sd card in the center console was still accessible from the car's screen after my phone key automatically unlocked the car.

I use this reader/adapter (you need to order an sd card with it). AFAIK, the Samsung PRO Endurance has the best environmental and endurance specs but the one that comes with the read/adapter should be fine and should be much better than all or almost all usb drives and ssds.

If the lack of usb access is a problem for anyone, then I recommend trying an sd card with adapter. This is what I've been using for a while in my glovebox for TeslaCam after my Samsung T5 ssd died prematurely. There have been many posts here about the superiority of a good sd card for the TeslaCam device so I won't repeat them here. Throughout this ordeal I've had problems with normal usb flash drive in the center console for my music but the sd card in my glovebox has always worked just fine.

Others have reported their glovebox device worked but the music device in the center console failed. I thought that perhaps they too may be using an sd card in the glovebox.

I find this idea of low and slow (power and lesser transfer rate - but still exceeding spec needed) interesting. In my vintage M3, I don't have the glove box data port. I only have the dual USB-A ports in the forward console and need to use a USB splitter to have drive and charge port available for one side of the wireless Tesla charge pad. I also like the idea of the Endurance Micro SDXC. On my existing Samsung 128GB flash drive (just like the Tesla version) suddenly last evening the car generated transitory notifications every few minutes for hours. Making a whole page of notices with corresponding Service Mode notices. Then stopped overnight. None on wake up until I unplugged my splitter then replugged and more messages. I have now temporarily put the Flash directly into the USB-A port without using a splitter and will see what happens. Tried this months back with no change however with much later software there may be a change. Anyway a suggestion for splitter would be helpful. I have been using this one. https://www.amazon.com/Splitter-ROÉ...refix=usb+a+splii,electronics,105&sr=1-9&th=1

 

[ElectricAnt54]

Here is what has been making my center usb ports detect devices. My glovebox usb-a has been working fine. I typically get 1 UI_a112 error per day. Vehicle software 2024.14.9 .

1) before manually opening the car door, use Tesla mobile app to wake the car by unlocking door via app & I turn on the HVAC.

2) do this each time you need to enter vehicle.

This has gotten my usb-c usb stick recognized again as well as usb-a game controllers using a usb-c adapter.

 

[BitJam]

Anyway a suggestion for splitter would be helpful.

For my 2021 MY with usb-c ports I use a hub like this which I really like. For you I would suggest looking into something like this TAPTES USB Hub 5 in 1 Ports for Tesla Model 3 Before June 2020 but I have no first hand experience with it.

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