Downgrading Tesla firmware on MCU1


May, 2023

Tesla | Firmware | Downgrade

The newest firmwares on MCU1 are extremely restricted in terms of functionality. In this guide I will show you how to downgrade your firmware and gain back control over your car.

Features like factory mode and dev mode has been blocked on newer firmwares as well as the ports 4030 and 4070. A bunch more stuff has been locked down and it makes DIY projects and tinkering a huge headache.

Before you start this upgrade I HIGHLY recommend that you have a female fakra to ethernet and a male fakra to ethernet cable as well as an RJ45 coupler. I had these made for me, but the pinout can be found below. This will make access in the future a million times easier since you don't have to take out IC. For the ultimate solution, check out the Tinkla Buddy. Seriously, it's a must have for MCU1 owners and it includes the cables and RJ45 coupler.

Fakra pinout.


Downgrading requires connecting your laptop up to the car tricking it to thinking your laptop is the instrument cluster. To be able to do this you have to take out the IC and this requires some screws to be removed. I won't go in depth here on how to do it since the service manual is free over at You can also just check out this YouTube video for a how-to. 

When you have the back of the IC accessible you can take out the fakra that goes into the IC and plug that into the fakra cable you had made. Then you plug the other fakra cable into the back of the IC. This will leave you with two RJ45 ports which you can use the coupler to have IC and CID talk to each other. However, in this case, you can take the CID cable (the one you unplugged from IC) and plug it into your laptop.

Getting connected

Your PC has to have a static IP-address of This is the IP address that the IC has and setting this on your PC will allow it to talk to the rest of the car. Subnet is and gateway left blank. You will now get connection here and can ping


Hosting firmware file

You need to host the firmware file on an http server. This has to be http and not https, and you have to specify the http port in the url when installing. The server does not have to be local, but it's smart to test the URL in a web browser to see that it automatically downloads and you aren't being redirected to https or that there is a cookie popup.


Make sure that your car is on a solid Wifi network. This can be hotspot from your phone as well.

Make sure you have telnet installed on your device and then do "telnet 25956" and you will be met with the Tesla Cid-updater. 

Here you can run the command


After pressing enter in cid updater, quickly connect the RJ45 cables together so the IC can talk to CID again. Then go into the Software tab on the car and it should start a download. It will show progress, but may take a while depending on your connection and server.

If it doesn't start downloading after a bit, I would scroll-wheel reboot car and try again.

If the downloads stalls for a long time or fails. I would reboot and then run "reset" in cid updater and try again.

Don't lose hope if it takes a few tries. It will work eventually :)

I recommend leaving the software tab open and staying in the car while it downloads. It will also show as downloading on the app, but staying in the car ensures it's active and you can montior progress. The green bar will go all the way to the right side of the screen. When it is done it will stage an update automatically and give you the orange icon. You'll get a notification in the app as well.

You can then install the update and let the car do its thing. When it boots up you will now be on 2022.8.10.5!

You can now access the blocked stuff again and have fun with factory/dev mode. I will probably make a guide on how to get into these modes in the future.

In case you want to go back to the newer firmware, Tesla will push this down your throat so the car will always nag you to install that one. To kill that update, you can type "reset" in the cid-updater and it will be gone temporarily. 

IC disassembled from Model S.
Downloading firmware.

Best of luck on the downgrade. Have fun and reach out if you need assistance :)

Copyright © Vegar Henriksen | Built using Google Sites | Terms of Use | Privacy Policy