Upgrading / Modifying / Fixing

CASE CLOSED: eMMC chip failure, what is it? should I be worried? what can I do?

Last modified: 2021-09-14

11 min(s) read

For continued updates on this issue please read this

Similar to door handles problems with Tesla Model S, a new wave of concern has grown over the MCU and its eMMC chips failing prematurely. This currently only affects vehicles which have an MCU1 (i.e. cars older than March 2018), which MCU do I have?

What is the actual issue?

MCU 1 has 8GB (Hynix) of soldered-on flash / solid-state memory card which is located on a smaller daughterboard – All Tesla cars built before March 2018 have this chip and like all flash memory it only has a certain number of writes before it will slow/fail, effectively Tesla have been writing logs to the chip too quickly which has caused <we don’t have an exact number> of them to slow down or in some cases cause the main screen to completely die.

What is being done about it?

We have various updates from Tesla on this issue but the main points are as follows:

UPDATE: Refunds now coming through – CASE CLOSED

UPDATE: Reimbursement information released for those that paid for 3rd party upgrades

UPDATE FEB 2021: We issue a statement

UPDATE JANUARY 2021: Tesla are asked by NHTSA to recall those cars affected, they have 2 weeks to make a decision. This basically would mean even those past the 100,000-mile new warranty limit (as sorted in November 2020) would be able to get a FOC repair/replacement. Normally Tesla UK will mimic/copy a US decision like this.

UPDATE NOVEMBER 2020: Tesla publicly announces fundamental changes to the warranty to address the situation. We continue our two way conversation with Elon and thank Tesla for finally sorting. We thank the teams in the UK and EMEA that also pushed this issue for us.

UPDATE OCTOBER 2020: We now advise any members affected to take it legal with Tesla if they believe this isn’t being suitably addressed as per the details below – Note: Paid Supporters get 10-minute free consultation with London Law Firm here – We also publish a letter which can be found here.

UPDATE SEPTEMBER 2020: MCU2 replacements are available for vehicles with AP2.x and Tegra MCU1s at a cost of £2000 + VAT

UPDATE SEPTEMBER 2020: Daughterboard upgrades are now available in the UK for £314 all in. Note: We as a club still believe this should be a Free of Charge repair / recall and we will continue to push for this, however, it’s still a welcome change.

UPDATE AUGUST 2020: Tesla will soon offer a daughterboard upgrade (a smaller section of the MCU1 which holds the eMMC on) for European vehicles, which will mean those having a failed MCU due to the eMMC wear won’t be faced with a £2500, £1800 or £980 bill but one closer to £300 (final pricing not confirmed, it’s based on a $340 repair bill we’ve seen in the US).

UPDATE AUGUST 2020: In the US daughterboard (a smaller section of the MCU1) upgrades are now an option at around $340 these replace the area with the eMMC chip on, it’s unknown if they’re upgraded 64GB chips or not, we’re hopeful a similar option will become available for the UK. MCU2 upgrades are also happening in the US for $2500, no firm date from these upgrades to take place in the UK but it was stated end of Summer. Further info on MCU2 replacements (US only for now).

UPDATE JULY 2020: Tesla has reduced the cost of an upgraded 64GB remanufactured MCU1 to £920 (inc VAT) + Labour (~£150) this is a reduction from the previous £1800-£2500 owners were being charged. We’re told Tesla are working to reduce this price further. Tesla has also worldwide lowered the warranty period on replacements units from 4 years to 2 years or 25,000 miles whichever comes first. For a full list of what we’ve done to date and the responses back from Tesla please visit here (you will need to login).

UPDATE JUNE 2020: Tesla will now fix this for ~£1000 + Labour and will upgrade the chip to 64GB, Tesla are working to reduce this price further. A further update from Tesla was provided, click here [or Facebook] to read (need to be logged in)

Tesla can fix the issue but will charge you £1800-£2500+VAT + Labour to replace the whole MCU instead of just soldering on a new £20-£50 chip.

In all cars built after March-May 2018 (if you’re unsure read this or if you have Netflix or games like Cuphead you’re not affected) the chip was upgraded to a higher capacity so it’s much less of an issue.

A few more quotes from experts (from this article) on this:

“The main issue is that this excessive log file writing causes eMMC flash wear. Flash memory is generally only rated for some tens of thousands of write cycles. What happens is that the flash memory starts to fail when writings can no longer be completed. When one block fails, parts of the firmware may also become unreadable, leading to poor operation or failure of the MCU completely.”

“The filesystem in MCUv1 is handled on a NAND-based eMMC flash chip. Although these are solid-state and great for automotive use, there is one pretty serious drawback. Each memory bit on a flash chip can only be written to a limited number of times before data gets corrupt – and that bit can no longer reliably store a 0 or a 1.”

“Tesla selected a flash chip that is unable to handle the constant read/write functions.  These chips have since been replaced with a more robust version.”

What have Tesla said so far on this

Within our meeting with Tesla it was stated that:

The highest level of engineering looking into it to stop the problem happening rather than to repair.

Currently, Tesla’s stance seems unchanged, sadly it is a full MCU change if yours fails, we raised the fact this goes against Tesla’s mission as nobody wants to see a computer being scrapped over a ~£20 component, it would seem it’s down to Tesla US to solve this. Cars will continue to be addressed on a case by case basis.


Tesla have also said:

“Tesla continually improve all aspects of the vehicles firmware. Some of these will include life-extending enhancements, customer feature advancements and core level updates. The core level updates along with the life-extending enhancements, will not necessarily be noticeable to the owner.”

Can service departments gauge the status of an eMMC chip?
The service department have access to multiple automated diagnostic tools to investigate issues experienced by the customer however, we do NOT have a tool to check the overall health of the eMMC. Infotainment engineers may have limited access to interpret some data from the memory, but this is not shared with nor is it needed by service technicians.

What has Tesla Owners UK done to help?

A full list of everything we’ve done to date on this can be found on this page (note you will need to be logged in to view).

We keep requesting Tesla UK manages this problem proactively without owners having to fight and request cover under Consumer Law constantly. We will continue to maintain pressure on Tesla to fix these issues during our meetings. We’ve also put together this document which lists 3rd party companies that can do the work for less than Tesla would do it. We’ve increased the information about Consumer Rights Act 2015 and Sales of Goods Act on this page as well as adding all warranty documents for all cars.

What has actually happened to fix this?

Software changes have gone out to reduce the logging of data to these chips, this reduces the damage the software is having on the chip, however, the issue appears to still be a concern for many owners, especially owners that want to keep their cars for 10+ years.

I’m confused can this be explained better?

Sure watch this video (from 8:41), read this & read this

UK consumer law is pretty clear so worst case this should protect owners but what exactly protects me?

In short, a product should last a reasonable period for the expected length of ownership of the product. We suggest the following action if you’re concerned:

  1. Request a remote diagnostics from Tesla if you’re seeing slower than previous MCU
  2. Request to find out the MCU health
  3. If it’s failed or failing request a replacement/fix
  4. Cite consumer law if required
  5. Escalate using these methods if you believe the service manager of your service centre has failed to help you when it should be sorted under consumer law.
  6. Take Tesla to court over the issue if required or https://www.gov.uk/make-court-claim-for-money or https://www.moneyclaim.gov.uk/web/mcol/welcome

Is there anyway Tesla can give an indication to an owner of MCU health?

We’ve not heard an official answer on this but at least one owner was told the % health of his eMMC/MCU. So if that’s the case with you request a service appointment and escalate it using this method (listed at the bottom).

What are the signs?

It’s hard to give exact answers here as some problems could be simply problems with the latest software update, that said the following are known symptoms from owners that have had complete failures:

  • Sluggishness of the systems
  • Reboots occurring spontaneously
  • Browser slower than ever
  • Problems rendering maps
  • Reboots start to take longer – several minutes
  • After each reboot, some features would be broke
  • In the end, reboots would take up to two hours and…

The final sign you have a problem is a main screen dead and no reboots fix it.

Update: You can view the data from our members that had the issue here.

What can be done about it?

  1. You wait for it to stop working and get it fixed under warranty (if you’re still within warranty)
  2. You wait for it to stop working and get it fixed under UK consumer law (e.g. Consumer Rights Act 2015, as explained on this page.
  3. You proactively get a 3rd party to replace the chip (Warning: doing so could void any existing warranty) – Discounts are available for this on our supporter discount page
  4. You pay Tesla for a replacement MCU1
  5. You pay Tesla for a replacement MCU2 (when they eventually allow it)

What are the risks with paying for a 3rd party upgrade?

  1. If the chip has already failed it will be impossible for the 3rd party company to replace as they need a copy of the files/certificates on the chip, if yours has failed the only method is to speak with Tesla unless you’re happy with no app access and no further software updates, ever!
  2. If the certificates can’t be read from the failing chip and you get a repair from a 3rd party, Tesla won’t help you with sorting new certificates to the new chip (they will however if you buy a brand new MCU from them mind you).

What companies are offering 3rd party replacement chips?

NOTE: We suggest everyone speaks to Tesla first to address the issue, if a service manager doesn’t wish to sort then please escalate using this method. Modifications to your Tesla may invalidate all or part of your warranty and may change the characteristics of your vehicle or could change the way future issues are handled with your vehicle. Your Tesla paperwork will provide the latest information on this but it’s important to remember that generally “Installing non-approved parts and accessories, or performing non-approved modifications, can affect the performance of your Tesla and the safety of its occupants. Any damage caused by using or installing non-approved parts, or by performing non-approved modifications, is not covered by the warranty. Tesla does not accept liability for death, personal injury or damage that occurs if you use or install non-approved accessories or make non-approved modifications.” So please check your warranty paperwork, with Tesla, with the company providing any services and do your own independent due-diligence checks and research before proceeding with any modifications to ensure that any good or service offered is suitable for you and your vehicle before proceeding, Tesla Owners UK Limited offer no warranties, no endorsements (express or implied) and accept no liability howsoever or whatsoever arising from use of this page or any discounts associated with it.

  • Gary at EV LINK [there is a discount for Tesla Owners UK Supporters] in Milton Keynes / Buckingham (expect to pay £500-£650 for a 64GB upgrade with a 12-month guarantee) – Several UK owners have used this service and recommend it
  • Laadkabelwinkel (often this is a Swissbit 64GB industrial grade eMMC) – Non UK

The price seems to vary depending on how corrupt/degraded the chip is. Bad chips may take twice as long to fix, which will increase the labour costs. Considering Tesla’s cost to replace the whole unit this should be a cost-effective approach for those outside of warranty and/or outside of the 6 year Consumer Rights Act 2015 protection. It’s not clear what warranty (if any is provided)

We will update once we know of any other UK locations offering this service.

Further reading/watching:


Do you have the expertise? Share your knowledge!

Remember modifying your vehicle may invalidate part of your vehicle’s warranty.
Therefore, be careful and check with Tesla if unsure. Also any modifications will most likely need to be OK’d with your car insurance company.

To the best of our knowledge, these guides are correct and factual. However we take no responsibility if something does go wrong.

If you spot a mistake please ensure you alert us.