macOS Monterey 12.3 Update Bricking Macs That Have Had Logic Board Replacements

The latest macOS Monterey update, released to the public this week, is bricking Macs that have had their logic boards replaced, causing panic among customers who are unable to get their Mac back to a working state, according to a cluster of user reports posted on social media.

Universal Control was one of the things that Apple brought to users. Not all users are able to experience the latest update or Universal Control.

Users who attempt to update their Mac to macOS 12.3 from macOS 12.2.1 or earlier are met with errors, endless restart loops, and possibly a completely bricked Mac according to an Apple Developer forum thread. There are only reports on Macs that have had their logic boards replaced.

There is a firmware bug in Mac OS 12.3 that renders the update impossible to install on any 2021 14 or 16 inch MacBook Pro that has had it's logic board replaced.

The cycle is:

You try to upgrade, the upgrade will fail but recovery to handle it correctly, you'll reboot still on 12.2.1 but with a report a problem dialogue informing you of an iBoot PanicYou'll try to upgrade again. This time, the iBoot FW will corrupt. You'll see the apple icon flash on boot 5-6 times before seeing the exclamation mark symbol telling you recovery is needed.You can try and revive using a second Mac with Apple Configurator 2. This will fail, because it tries to load the 12.3 firmware from the IPSW, in either DFU or Recovery mode.

The only way to get things running again is to manually download the 12.2.1 IPSW and use Apple Configurator 2, with the Mac in DFU mode, to load the revive image. This will update the firmware of iBoot, and the recovery image to a working build. The Mac will then restore 12.2.1's OS, keeping your data upon finishing.

There are two possible outcomes users are facing. Either a Mac becomes completely bricked and unusable, or a Mac completes the update process and restarts but doesn't update and displays an iBoot Panic message.

There is an error message on a 14-inch MacBook Pro.

A thread on the internet reports similar issues.

If the Mac doesn't boot up after the update sequence, users need to revive it manually. Users need a second Mac to revive their bricked Mac. Many customers only have one Mac, or no compatible Mac, so they have to go to the Apple Store for help.

Staff at the Apple Store will likely replace the faulty logic board with another logic board, putting users in an endless loop until the bug is fixed. Users are generally reporting mixed results when trying to put their Mac into DFU mode.

Any attempts to get 12.3 on your mac will fail with that error.

You should be able to get into DFU though - wait until you're on the exclamation mark screen after a few flashes, then do the DFU key sequence. Configurator will let you try a revive in recovery mode though, but not sure if that works - I assume that's your 21 error. You should get a 2006 error when trying in DFU mode.

The second time I tried a normal in system upgrade, the screen refused to show anything as a result of the firmware failure - but it still appeared in Configurator and the DFU key sequence still worked.

There are reports on the MacRumors Forum, with one user saying that they can't install macOS 12.3 in any way: direct upgrade, install via App Store, Recovery Mode, DFU Restore, all failed. All versions of the operating system work. I need to download the IPSW files for macOS to use it, but Apple only offers the files for macOS updates, so I have to install them on a bricked Mac.

There are instructions for reviving an Apple Silicon Mac and an Intel-based Mac here. We have reached out to Apple for comment and will update accordingly, but so far they have not commented or acknowledged the issue.