Did a macOS Update Brick your T2 Mac? I will Show you how to Boot your Mac into DFU Mode so you can Restore BridgeOS.

UPDATE 04/10/20: I am looking into some different reports  of the macOS Catalina 10.15.4 Supplemental update bricking T2 Macs. Users are reporting that the Mac will not turn on after the update (the Mac will act like it’s dead). This issue could very well be just a fluke on a few Macs, but I will keep an eye on it. If your Mac has one of the following symptoms below restoring BridgeOS on your T2 Mac might help you.

This article will go over how to restore BridgeOS on your T2 Mac. This is not something that you will ever normally have to do. Restoring or reinstalling BridgeOS firmware would only be needed in the following situations.

• 1. Failed macOS Upgrade
• 2. Failed macOS Combo or Delta Update
• 3. Failed macOS Security Update
• 4. Failed macOS Reinstall
• 5. Failed BridgeOS or Failed Firmware Update
• 6. “Command Option R” fails to boot your T2 Mac to the newest version of macOS Internet Recovery. (Example: 10.14 is out but the Mac boots to 10.13)

This link shows the different ways you can boot to the Recovery Partition or Internet Recovery support.apple.com/en-us/HT204904

Typical symptoms that you might see that would indicate a failed or bricked update.

• Mac Seems dead
• Will not turn on
• Black Screen
• No Fan Noise
• Power on LED Light does not turn on (Mac Mini)

If you find yourself in one of these situations you can follow the instructions below.

Article Table of Content

• 1. Warning!
• 2. List of T2 Compatible Macs
• 3. Setup and Cable Requirements before you begin
• 4. Download Apple Configurator 2 app
• 5. How to Boot your T2 Mac into DFU Mode
• 6. My Instructions for the MacBook Pro & Air
• 7. My Instructions for the Mac Mini & iMac Pro
• 8. You made it! Apple Configurator 2 Screens
• 9. Begin BridgeOS Restore
• 10. Troubleshooting DFU Mode & BridgeOS Update Problems

1. Warning!

(Warning #1) Please keep in mind that the following instructions are for if your Mac will not boot or is in any of the 5 situations listed above. Performing these steps should only be used if you have exhausted all normal troubleshooting techniques. If you are just messing around and something goes wrong (USB Cable becomes disconnected in the middle of the update for example) you could brick your Mac be forced to bring it in for service!!!

(Warning #2 – Do not attempt a BridgeOS if you have a Beta version of macOS installed on your Mac) I had problems with this process on one of my test Macs. One of my test devices failed in fantastic fashion. What I thought happened was the BridgeOS update just failed on a fluke. What really happened was Apple Configurator 2 attempted to downgrade BridgeOS from a higher Beta version of Catalina BridgeOS down to the Production version of Mojave (Catalina was not released yet). When Apple Configurator 2 attempted to downgrade on the 3rd step it failed leaving the Mac in a Unusable state. Apple does not allow downgrading BridgeOS. 

After the production version of BridgeOS was released for 10.15.0, I was able to restore that MacBook Air! To review, DO NOT try a BridgeOS restore if you have a newer Beta Version of macOS installed on your T2 Mac!

Hat Tip goes to Eric Holtam @eholtam for helping me connect the dots on why my 10.15 test failed.

2. List of T2 Compatible Macs

This is a list of T2 Mac that you can can have BridgeOS restored.

• 2019 16″ MacBook Pro
• 2018-2019 13″ & 15″ Macbook Pro
• 2018-2020 MacBook Air
• 2018 Mac Mini
• 2017 iMac Pro
• 2019 Mac Pro

3. Setup and Cable Requirements before you begin.

You will need to meet the following requirements – 

(The Host Mac will do the work and the Target Mac is the Mac you need to Restore)

• 1. USB-C Thunderbolt 3 Equipped MacBook Pro as the Host Machine.
• 2. The Host MacBook pro must have at least macOS 10.13.5 and Apple Configurator 2.6 or newer installed.
• 3. Internet access on the Host Mac – “You may need to configure your web proxy or firewall ports to allow all network traffic from Apple”
• 4. Thunderbolt 3 (USB-C Cable that has the lighting bolt on each side) OR Apple USB-C Charging Cable or USB-C Cable. (USB-C Cable MUST Support Power & Data)
• 5. The Host Mac can have the cable plugged in anywhere.
• 6. The Target Mac MUST have the USB-C Cable Plugged in to the Left Hand side USB-C port. This is First port in line (Port closest to the front of the Mac or trackpad) If you are still confused look at the picture below.
• If you don’t meet all the prerequisites booting to DFU Mode will FAIL.

4. Download Apple Configurator 2

https://i1.wp.com/mrmacintosh.com/wp-content/uploads/2019/09/Apple-Configurator-2-App.png?resize=300%2C140&ssl=1 300w" sizes="(max-width: 595px) 85vw, 595px" data-recalc-dims="1">

If you do not have Apple Configurator 2, you can download it now from the Mac App Store with this link.

https://apps.apple.com/us/app/apple-configurator-2/id1037126344?mt=12

5. How to Boot your T2 Mac into DFU Mode

With all the startup keyboard commands you can issue a Mac, booting into DFU Mode should be pretty simple right?

NOPE!

You have to follow a very particular sequence to get this to work. I have attempted to find the exact way to get this to work every time. Even then sometimes the system will refuse to Boot into DFU mode.

Apple’s Instructions

You can find Apple’s instructions for booting into DFU mode here.

help.apple.com/configurator/mac/2.7.1/#/apd0020c3dc2

6. My Instructions for the MacBook Pro & Air

Bottom line, it’s hard to get your T2 Mac into DFU mode. You could try Apple’s instructions 10 times and STILL not get into DFU mode.

Once you have meet all of the pre requisites above, follow the instructions below to get into DFU Mode every time.

• 1. The Target Mac must be OFF to begin.
• 2. Press the Power button and hold for 1 second.
• 3. While STILL holding power immediately hold down RightShift, Left Control and Left Option.
• Hold down all 4 keys for 8 Seconds (count 1 one thousand) then let go of all keys.
• You will not see anything on the Target Mac screen. 
• Keep an eye on the Host Mac’s Apple Configurator 2 Application. The App should say “Connect Devices”
• When the Target Mac is booted into DFU mode correctly, the host will show a big DFU icon in Apple Configurator 2. 
• After you see the DFU picture pop up on the Host Mac you can let go of the keys.

7. My Instructions for the iMac Pro & Mac Mini

The 2018+ Mac Mini and 2017 iMac Pro are a little different yet are super simple to get into DFU Mode.

• 1. Disconnect the power cord from the iMac Pro or Mac Mini. 
• 2. Plug USB-C/Thunderbolt cable into the USB-C port next to the Ethernet Port.
• 3. Plug the other end into the Host Mac.
• 4. While holding down the power button, connect the iMac Pro or Mac Mini to power and continue to hold the power button for about 3-5 seconds
• 5. You should now see the DFU logo on the Host Mac.

8. You made it! Apple Configurator 2 Screen

The hard part is now over. Now we can restore BridgeOS on the Target Mac. When you first open Apple Configurator 2 the screen will look like this.

Once your Mac is booted to DFU mode, you will see this screen on Apple Configurator 2. You are now ready for the next step.

9. Begin BridgeOS Restore

You are now ready to restore BridgeOS on the Target Mac. Click Action from the menu bar then Restore.

https://i2.wp.com/mrmacintosh.com/wp-content/uploads/2019/09/DFU-Actions-Restore.png?resize=193%2C300&ssl=1 193w" sizes="(max-width: 172px) 85vw, 172px" data-recalc-dims="1">

You will now see a warning message. Do you want to restore and update “iBridge” to the latest firmware version? You cannot undo this action. This means that once you update BridgeOS/iBridge you cannot go back to the previous version.

Click the Restore Button to begin. Step one will download the latest BridgeOS update from Apple.

Step 2. Unzipping BridgeOS

Step 3. Installing BridgeOS Update.

Finishing Up

The entire process will only take about 4-10 Minutes. Most of the time is spent downloading the 400-600MB BridgeOS Update. The Unzip and Install parts only take about 1 minute each. When complete the Mac will automatically Boot up.

10. Troubleshooting DFU Mode & BridgeOS Update Problems

• I can’t get my Mac to boot into DFU mode. This is the toughest part of the whole process as I mentioned above. Keep trying the steps I listed above. Sometimes it takes multiple attempts to get his to work.
• You can use System Information to see if the USB-C port lists your Mac in DFU Mode.

• BridgeOS Restore Error (UPDATE: This could happen when you try to restore BridgeOS on a macOS Catalina 10.15 Beta System) – The OS Cannot be restored on this device. The Operation couldn’t be completed. (AMRestoreErrorDomain error 79 – Failed to handle message type StatusMsg) [AMRestoreErrorDomain – 0x4F (79)] – If you get this error it means that the BridgeOS updagte has failed and is unable to complete. The system will be unable to boot. When powered on the screen will be black. The Mac will have to be brought to an Apple Store for Service.

Apple Configurator 2 Reports RECOVERY instead of DFU Status.

• If you see RECOVERY this means that BridgeOS is unable to boot and is the default status when you power on the Mac. 

If this happens you can try getting a different Mac as the HOST. When I used a second Mac the BridgeOS update went through! Not sure what could have caused the issue the first time but it worked.