Model S/X MCU1 (Tegra): eMMC wear — prevention and recovery

Symptoms

• Freezes, reboots, black screen, loss of rear camera/HVAC controls/turn signals on screen.
• A badly lagging interface (even the volume control responds late) is the final stage of wear.

⚠️ Two things you must not do at the first symptoms

If your MCU1 already shows signs of eMMC wear, then until it is repaired, never do the following:

1. Do not install OTA updates. Writing a large amount of data to a worn eMMC carries a high risk of a permanent black screen and the loss of the Tesla certificates. Once the certificates are gone, the repair becomes many times harder (t.me/teslacar_chat/124479, Vyacheslav Pro: "one of them had memory in such a state that the certificates were lost").
2. Do not reboot the car unless you have to. Every write cycle brings the eMMC closer to the end. "Wait, and for God's sake don't reboot the MCU" (t.me/teslacar_chat/248485).

The community puts these two rules on a par with "don't drive drunk": real people lost their MCUs exactly this way.

What to do

• Preventively replace the eMMC with 64–128 GB at a specialized service.
• Or officially, via the campaign/improved board (MCU repair).
• On an XP100D and other S/X with Tegra, consider an MCU2 retrofit (t.me/teslacar_chat/367544: Tesla often refuses to do it officially, so owners look for third-party shops).
• In Moscow the chip is resoldered as a "semi-official" repair (t.me/teslacar_chat/467924, Tesla Moscow service: "fixed by resoldering the memory chip in the MCU").

Price in Belarus

≈ $250–600 for chip replacement with data transfer (turnkey: remove the MCU, resolder, refit, restore the software).

💡 Where this figure comes from: the reball engineer's labour alone at an ordinary electronics shop is 1,000–2,000 RUB ($13–25), while on the MCU itself the same work then comes to ~30,000 RUB ($350) (t.me/teslacar_chat/182032). The rest covers removing and refitting the MCU, migrating the data and restoring the firmware. If you don't like your shop's price, ask for a breakdown by stage.

⚠️ If the resoldering shows the eMMC is already dead (corrupt firmware, no boot), the job also needs a restore from a backup or a donor, which costs extra.

Links

• Tesla eMMC FAQ: https://www.tesla.com/support/8gb-emmc-recall-frequently-asked-questions
• NHTSA recall documents 21V035: https://static.nhtsa.gov/odi/rcl/2021/RCRIT-21V035-9972.pdf , https://static.nhtsa.gov/odi/rcl/2021/RCLRPT-21V035-4682.PDF
• MCU1 problem explanation: https://www.findmyelectric.com/blog/tesla-mcu1-emmc-failure-explained/

Community experience TESLA Belarus

Analysis of 400,000 messages from the TESLA owner's group BELARUS chat: relevant for early Model 3 and Model S/X with MCU1.

Solution options from chat (with Belarus nuances):

1. MCU from a donor (~$1000 + labor). Downside: a different VIN displayed on screen, may be cross-checked at inspection and at the border.
2. Resoldering the eMMC chip: cheaper, but you need a specialist with the equipment.
3. In Poland it is more expensive, but the original VIN is preserved.
4. After MCU replacement, updates may not arrive if VIN doesn't match.

Who reported the issue: AA, alex

Who found the fix: Иван, Alex Bor, Dr. Pilulkin, Андрей Ковалёв

Discussion in Telegram: #214855, #214858

Additional sources:

• Consolidated eMMC Thread, MCU repair (Tesla Motors Club): https://teslamotorsclub.com/tmc/threads/consolidated-emmc-thread-mcu-repair-black-center-screen.181124/