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MCU fails for the second time

The MCU (the main 17" touch screen and computer unit) on my 2013 Model S has failed for the second time, this time out of warranty. The first time Tesla replaced it under warranty, but this time it's costing me more than $3,000 ($2726 plus tax) - about as much as the top of the line MacBook Pro. The service center told me that the "processor" had failed inside the MCU. I live in Seattle, where temperatures are not extremely hot (in general), though I have driven it around the country and to hot places (not often). I bring this up to the group because I certainly hope this won't become a regular failure every 2-3 years for everyone. And while my car is out of warranty, it just feels wrong (as it does when other car companies cite the warranty in similar cases) to have to pay to fix something that seems like an intrinsic defect. The MCU is innovative - not a standard automotive computer, but a Linux-based system of Tesla's creation (though I think Foxconn makes it for them). It should be robust to many years of driving, not subject to regular very expensive failures. Am I wrong?
 
I escalated one level above the service center person I was dealing with, and asked, but they said it could not be covered under goodwill because it was out of warranty and my car is high mileage. I can see that, if it were something that would degrade with high mileage, but this is a CPU, and its lifetime should be a function primarily of temperature and age.

I can't pursue this any higher before getting it fixed, because without it, the car is an oven (no A/C), can't open the garage, can't respond to the mobile app, can't navigate, etc. It's like my first car: a 1975 Toyota Corolla with busted HVAC.
 

shokunin

Active Member
Supporting Member
Feb 28, 2012
1,216
653
Irvine, CA
The MCU/Touchscreen is going to be a sore topic for a long time coming. I'm 2/2 for bubbles on the touchscreen, all replaced under warranty but the fact theres little you can do since it controls all the hvac, stereo, nav, settings, controls for the car. Plus it's not like you can just find a spare part from a salvage and pop in a new replacement without reflashing the chip.
 
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MP3Mike

Well-Known Member
Feb 1, 2016
19,958
49,964
Oregon
I escalated one level above the service center person I was dealing with, and asked, but they said it could not be covered under goodwill because it was out of warranty and my car is high mileage. I can see that, if it were something that would degrade with high mileage, but this is a CPU, and its lifetime should be a function primarily of temperature and age.

@andyrebele I think there are two main failures with the MCU:
* The bubbling/leaking of the screen. (This part can be replace separate from the entire MCU and is cheaper.)
* The MCU stops working completely, which is normally because the flash storage has worn out because of excessive logging/writes.

So if your failure is because of the worn out flash storage, it is directly related to mileage and not temperature/age. As every mile driven is more data logged which uses up the limited write capacity of the flash.

My understanding is that Tesla has reduced the logging/writes in more recent firmware versions, but @Ingineer disables a lot more of the logging unless it is actually needed for debugging to make the flash/MCU last a lot longer.

If you get your MCU replaced and they put in a remanufactured one, where like maybe they repaired just the screen, I wonder what the chances are that they replace the flash too, or could you end up with one that has most of it's life already used up...
 
I am at 108,000 miles and I have not had any problems with my MCU. I currently live in Arizona, but just since January of 2017. I have done road trips from California to New York, California to Washington, California to Utah, California to Nevada, California to Utah and Arizona to Texas.

Best of luck to you - I hope this one will last forever.

Brent
 
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@andyrebele I think there are two main failures with the MCU:
* The bubbling/leaking of the screen. (This part can be replace separate from the entire MCU and is cheaper.)
* The MCU stops working completely, which is normally because the flash storage has worn out because of excessive logging/writes.

So if your failure is because of the worn out flash storage, it is directly related to mileage and not temperature/age. As every mile driven is more data logged which uses up the limited write capacity of the flash.

My understanding is that Tesla has reduced the logging/writes in more recent firmware versions, but @Ingineer disables a lot more of the logging unless it is actually needed for debugging to make the flash/MCU last a lot longer.

If you get your MCU replaced and they put in a remanufactured one, where like maybe they repaired just the screen, I wonder what the chances are that they replace the flash too, or could you end up with one that has most of it's life already used up...

Very helpful, thanks for the insight.

So, since I have the old MCU, can I replace the flash and let someone else use it? Is the flash replaceable without major surgery?
 

appleguru

Active Member
Mar 15, 2017
1,104
1,921
MA, US
Very helpful, thanks for the insight.

So, since I have the old MCU, can I replace the flash and let someone else use it? Is the flash replaceable without major surgery?

Not really, from the photos of the CID that I have seen, the flash appears soldered on to the logic board. If that is what failed, even if you replaced it, you would likely be SOL, as you wouldn't have the raw firmware/bootloader on them to actually boot your system (unless you took the replacement chips from known good board and installed them on the same pads they came from).

Hard to say what actually failed on yours without doing some diagnostics though. Could be as "simple" as some blown caps, mosfets, inductors, fuses, etc. those are common "dumb" components that you could find equivalent parts for and swap out to get up and running again (in theory anyways).

Glad you're getting a yours back; I'd love to poke around with one/see if I couldn't get it working again and learn some of the inner workings at the same time (without having to take my car apart!)

If you take yours apart, I'd start by looking for anything that looks obviously failed. Start with the 12V input stage/power supply circuit and go from there, looking for anything that looks corroded, charred/burnt, shorted, bulging, leaking, etc.

If you see a fuse (likely soldered to the board if there is one), check continuity across it to see if it is blown.

TBH, I almost doubt it was your flash that failed. Tesla engineers are smart; they know the max write cycles of their parts and how to do proper wear leveling if needed. I very much doubt they would be stupid enough to exceed them on a car with less than 500k miles. Much more likely the power supply failed (the fact that you have gone through 2 CIDs does point at perhaps a larger systemic issue with your vehicle that could causing the early failure... would be very interesting to know the root cause of failure in both cases, though I suspect we never will).
 
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MP3Mike

Well-Known Member
Feb 1, 2016
19,958
49,964
Oregon
So, since I have the old MCU, can I replace the flash and let someone else use it? Is the flash replaceable without major surgery?

It can be done, but I think it is surface mounted so you would need a re-work station and some skills. On the other hand the screen could probably be taken off and put on a MCU with the bubbling/leaky problem with ease.

Out of curiosity how long ago was your MCU replaced, and what is your total mileage? I would still push to get them to cover it, since in all likelihood you got a refurb MCU that already had a significantly worn emmc/flash module. (You could always PM JonMc here on TMC.)

TBH, I almost doubt it was your flash that failed. Tesla engineers are smart; they know the max write cycles of their parts and how to do proper wear leveling if needed. I very much doubt they would be stupid enough to exceed them on a car with less than 500k miles.

We have seen a number of cars with this problem, and @Ingineer has helped a few people transfer their data to a salvaged MCU vs. paying Tesla to replace it.
 

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