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Bad MCU?

Feb 15, 2019
380
127
arizona
I have a 2019 M3 MR with approx 4500 miles.

On Sat Feb 21 2021 I got in the car and put in my pin and got warnings that the Brake Regeneration was not workng and the AutoPilot was not working and the Cruise Control was not working.

It was right.

I was going from E. Mesa to Sun City.

Eventually the braking began working and the cruise but the Auto Pilot never did kick in.
At one point the car lurched as though someone had taken their foot of the gas but I hadn't. There was a car on each side of me but nothing in front or back of me for hundreds of yards.

I have repeatedly had problems with these warnings and things not working.

I think I have a 2.5 MCU. I am wondering if it is defective. is there any way to tell for sure?

It seems I have read of some place that fixes the MCU's for a reasonable price but don't remember where. Mine < should > be under warranty I would think.
 

jjrandorin

Moderator, Model 3, Tesla Energy Forums
Moderator
Nov 28, 2018
12,481
14,867
Riverside Co. CA
Regen braking can "not work" for a number of reasons. The battery could be too full to accept a charge, the battery could be too cold to accept a charge, etc. Autopilot and cruise control can "not work" for other reasons as well, like dirty cameras / sensors, sun glare on some cameras etc.

The car could have tried to brake for any number of reasons as well.

TL ; DR .. nothing you list shows a problem with the "MCU". If you have Full self driving, you can get the new FSD computer swapped (version 3.0) in for your version 2.5. If you dont have FSD, then you will continue to have the 2.5 hardware. Because there are a lot of variables for the things you posted, nothing points to "the computer" being bad.

You can open up a service appointment, and task tesla to look at the logs. Maybe they find something. With that being said, everything you experienced can be explained by something else as well, so it doesnt automatically look like the computer is bad.
 
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Gasaraki

Active Member
Oct 21, 2019
2,325
1,615
Syracuse, NY
I have a 2019 M3 MR with approx 4500 miles.

On Sat Feb 21 2021 I got in the car and put in my pin and got warnings that the Brake Regeneration was not workng and the AutoPilot was not working and the Cruise Control was not working.

It was right.

I was going from E. Mesa to Sun City.

Eventually the braking began working and the cruise but the Auto Pilot never did kick in.
At one point the car lurched as though someone had taken their foot of the gas but I hadn't. There was a car on each side of me but nothing in front or back of me for hundreds of yards.

I have repeatedly had problems with these warnings and things not working.

I think I have a 2.5 MCU. I am wondering if it is defective. is there any way to tell for sure?

It seems I have read of some place that fixes the MCU's for a reasonable price but don't remember where. Mine < should > be under warranty I would think.

THe MCU only controls the multimedia display (and some other minor stuff) because it is the "Multimedia Control Unit". All important car functions are controlled by the other car computers so I doubt your MCU is causing your issues.
 
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