Replace damaged MCU 2020 Model 3

[Deep_Pockets6]

Hello there, my shop is currently working on a 2020 Tesla Model 3 with MCU version 2. The date of manufacture is 12/2019.

We are having an issue where the A2B bus is being shorted to ground. Resulting in the overhead microphone and rear amplifier not working.

We have purchased an identical used MCU, we are planning to swap the mainboards and reuse the existing modem.

I read in another forum that @McDangle was able to swap the MCU but the car had issues.

Does anyone have any suggestions/manuals/info?

 

[KyleDay]

You can’t just swap mainboards as the car keys (vehicle certificates for Tesla authentication and firmware) are locked to your specific car. Unless you have access to move the credentials via Tesla service software you can’t swap mainboards and make it work.

 

[Deep_Pockets6]

You can’t just swap mainboards as the car keys (vehicle certificates for Tesla authentication and firmware) are locked to your specific car. Unless you have access to move the credentials via Tesla service software you can’t swap mainboards and make it work.

Thanks for the info, heres some more info for context, perhaps there is another solution.

We were installing an aftermarket audio system, which somehow shorted the A2B audio bus output on the MCU. The A2B output on the MCU shows continuity with ground. Now, only the front surround speakers work.

Is there a way to reprogram the mainboard? The service manual is not available online. Will Toolbox 3 be able to do this?

We don’t want to shell out the thousands of dollars it would cost to repair through Tesla.

 

[karkrazy]

The service manual is not available online

Did you mean this? Has been available for free for awhile now.

Model 3 Service Manual | Tesla

service.tesla.com

Your path of least resistance may be to just replace the MCU with tesla. Good luck, and let us know how it goes.

 

[evrepair]

+1 you will need a brand new MCU.

 

[karkrazy]

my shop is currently working on a 2020 Tesla Model 3 with MCU version 2.

OP - has your shop worked with Tesla’s before, and have they installed aftermarket accessories like these before, in similar Tesla’s? Because if they haven’t, I’d say it’s on them for frying your MCU.

Tesla’s can’t be treated like legacy manufacturer cars… As a high-tech company, I’d be surprised if their firmware code is not encrypted/hardened, and limited to only their Engineering folks, not the service center techs.

 

[yutian]

The rear speaker seems to pass through the overhead microphone. You can check the circuit diagram of Tesla's maintenance manual. There is the answer. If you need to replace the MCU, you must transplant the CPU chip and gateway inside.

 

[tls]

There is the answer. If you need to replace the MCU, you must transplant the CPU chip and gateway inside.

I'm not sure this is so. It was definitely not so for MCU1. What was actually the case was that the eMMC storage chip that carried the vehicle's configuration data had to be transplanted (or, in the case of a failing eMMC chip, its contents needed to be read out and copied onto a replacement). If the CPU and gateway are serialized somehow on MCU2 that would be a substantial change.

Either way you would be in for some nontrivial surface mount resoldering work. This would be beyond the capability of most car audio shops I'm familiar with. I think you may have to own up to the problem and involve Tesla.