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Advice: Failed LTE/WiFi with MCU 1

neusmell

Member
Dec 16, 2017
11
7
Chicago, il
My issue is slightly different than the recent MCU 1 failures so I wanted to get some feedback from the hive mind about what's the best course of action.

I have a 2015 Model S 90D with about two weeks left on the warranty.

In early October the LTE and WIFI went out - it had been flaky for about a month prior (wifi not connecting/showing no bars), but the LTE still worked so I chalked it up to a bug and bad wifi connection because I live on the third floor and the weather had sucked. After it fully went out the MCU reboots constantly and sometimes just won't boot to screen (staying black for 20-30 minutes, which is my entire drive).

Service was convinced that it was an issue with a bad update, but the mobile tech: (i) couldn't do anything without a networking card and (ii) thought that the boot issues were related to it trying to spool up the networking interface and failing for the entire 20-30 minutes.

I finally have an appointment to go into a service center next week, so I'm not worried about the LTE card getting covered under warranty. What's going through my mind is if this is really just the LTE card and not the MCU. Does anyone have any experience with this and could say one way or another? Just want to make sure I'm prepared with questions/to pushback before the service appt. I'm really just worried that they'll say it's just the LTE card and then the MCU goes out on me a month later when I'm out of warranty.
 

possum22

Member
Nov 16, 2016
113
56
Mt. Isa, Qld
Push Tesla to replace the MCU, mine lost 3G coverage when the MCU rebooted itself & reset itself & lost all settings(back to default), my car(S85) 2 months out of warranty and only 22k km at the time. WiFi on mine stilled worked.
Make sure you turn off schedule charging or you won't be able to charge it, when the MCU finally dies. I had to trucked my car to Tesla ot get the MCU replaced, couldn't get them to do the LTE upgrade, got 12 mths/20k km warranty on thr replacement MCU.
 

whitex

Well-Known Member
Sep 30, 2015
6,700
8,039
Seattle area, WA
It could be MCU emmc dying (about the right age of the car). The problem is that reflashing the update (applying the firmware twice) may temporarily fix it, push its life just long enough beyond the warranty. Read thread on emmc dying in MCU1's.
Likely MCU Failure (MCU1 eMMC)
It's too late, my MCU1 Died....
Preventive eMMC replacement on MCU1

I'm not sure if there is any way to force Tesla to replace the EMMC under warranty if they can make it work for another few weeks or months, but you could ask.

PS> EMMC will die in MCU2 too, as well as Model 3, except:
  1. oldest MCU2 car is ~1.5 years old today, at that age even MCU1's were ok
  2. MCU2 has larger emmc, so it will take longer to wear it out (though not necessarily proportionally longer, as MCU2 has more crapware like games and other features which take up room on emmc, plus MCU2's are getting updates more frequently - all things which wear out emmc along with logging)
 

AustinP

Active Member
Apr 6, 2015
1,295
1,024
Belgium
I was able to supercharge after my mcu died last week, although i have scheduled charging.
Note that I have unlimited supercharging, so it always starts without any need for mcu interaction.
 

whitex

Well-Known Member
Sep 30, 2015
6,700
8,039
Seattle area, WA
I was able to supercharge after my mcu died last week, although i have scheduled charging.
Note that I have unlimited supercharging, so it always starts without any need for mcu interaction.
So without unlimited supercharging MCU is required to start supercharging? So all those cars Tesla has stripped supercharging are actually crippled more than people have realized, making MCU the single point of failure for one more thing?
 

BPeter

Member
Feb 2, 2019
708
1,065
Minnesota
It could be MCU emmc dying (about the right age of the car). The problem is that reflashing the update (applying the firmware twice) may temporarily fix it, push its life just long enough beyond the warranty. Read thread on emmc dying in MCU1's.
Likely MCU Failure (MCU1 eMMC)
It's too late, my MCU1 Died....
Preventive eMMC replacement on MCU1

I'm not sure if there is any way to force Tesla to replace the EMMC under warranty if they can make it work for another few weeks or months, but you could ask.

PS> EMMC will die in MCU2 too, as well as Model 3, except:
  1. oldest MCU2 car is ~1.5 years old today, at that age even MCU1's were ok
  2. MCU2 has larger emmc, so it will take longer to wear it out (though not necessarily proportionally longer, as MCU2 has more crapware like games and other features which take up room on emmc, plus MCU2's are getting updates more frequently - all things which wear out emmc along with logging)

MCU2 also has 50% of the flash storage unformatted, so wear leveling of the writes has a massive amount of room to work with compared with MCU1. If they leave half of the MCU2 flash unused it should last as long as the car.
 

NoMoGas

Supporting Member
Supporting Member
Make sure you document on the service request "suspected MCU failure" and stay on top of it. Note the symptoms of MCU failure and document ON YOUR SERVICE PAPERWORK any and all symptoms you are experiencing. If the MCU does go belly up "after" warranty, you'll have an argument that it actually started to go before. They'll know what you're doing and may just replace the MCU.
 

whitex

Well-Known Member
Sep 30, 2015
6,700
8,039
Seattle area, WA
MCU2 also has 50% of the flash storage unformatted, so wear leveling of the writes has a massive amount of room to work with compared with MCU1. If they leave half of the MCU2 flash unused it should last as long as the car.
Depending how much they write. Remember that with MCU2 the updates are large (lots of bloatware like games) and logging includes videos from autopilot (fleet learning Elon has been touting) - probably things like AP disengagement and high def mapping stuff cached for when your car is on WiFi. So, while I agree that unused space helps, increased load offsets some of that advantage.
 

.jg.

Member
Feb 27, 2018
448
375
Weston Super Mare, England
If the display is blank for 20 minutes and then works, it is likely that your eMMC is dying. I had exactly this issue, with MCU startups being successively longer at each startup or reset. Over a period of a few weeks, MCU booting initially took about 3 minutes but ended up taking about 2 hours. After each startup, diferent features would not work or not work properly. I am guessing that the system was performing file system checks before it could mount volumes in the eMMC and that these took longer as more elements of the eMMC failed. Ultimately, the MCU could not start at all and was replaced under warranty.
I previously had a failure of WiFi and Bluetooth, with messages along the lines of "Initialising" or ""Device needs service". This was resolved by Tesla re-flashing the firmware of the WiFi and Bluetooth modules (remotely, via the cellular connection).
 

AustinP

Active Member
Apr 6, 2015
1,295
1,024
Belgium
So without unlimited supercharging MCU is required to start supercharging? So all those cars Tesla has stripped supercharging are actually crippled more than people have realized, making MCU the single point of failure for one more thing?
I don’t know how a car without unlimited supercharging behaves in a mcu dead case. Hence I specified my context to not generalize.

We should have confirmation from someone with a dead mcu and no unlimited supercharging before concluding.
 

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