8

This still works for 2022.8.10.17

Please make sure you do not have any pending installs, even navigation. You can try to fight against these, but 9/10 times it will win over you and cause headaches. It is actually better to upgrade and then downgrade.

Before you start make sure you have the fakra HSD cable so you can connect behind IC. This cable is called 1013230-00-A and can be found via Tesla Service or via sites like Aliexpress. 

If you don't have this cable on hand you can just cut one end of an ethernet cord and plug the different wires into the correct pins on the connector. Janky but it works. You can see the pinout below.

I do highly recommend having proper male - rj45 and female - rj45 cables as well as a coupler to connect them together. It makes future access much easier.

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. It makes dev mode and factory mode a breeze.

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 service.tesla.com. 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 your cable which goes into your laptop.

Your PC has to have a static IP-address of 192.168.90.101. 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 255.255.255.0 and gateway left blank. You will now get connection here and can ping 192.168.90.102.

This is the last firmware files which has the ports open to easily access dev/factory and use Toolbox2

Here you can obtain a copy of the firmware file. Remember to unzip it.

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 this works properly as many people get stuck here. 

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 192.168.90.100 25956" and you will be met with the Tesla Cid-updater. 

Here you can run the command

install http://xxx.xxx.xx.x:80/tesla/2022.8.10.5.mcu1

After pressing enter in cid updater, quickly connect back everything like it originally was. This will allow the car to talk with IC and you should see a green download bar in the software tab. It might take a little while, but it should be almost instant. 

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 monitor 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. 

A more permanent solution? Drive you car off a cliff

Good luck, have fun - happy tinkering

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