Thunderbolt Display randomly stopped working with M4 MBP

[theMarble]

Hi, I've got a 14" M4 Pro MacBook Pro running both 15.7.1 and 26.1, connected in clamshell mode to a 27" Thunderbolt Display via Apple's TB3 to TB2 adapter. It's worked perfectly for almost a year, until one morning recently when the display refused to wake up.

Nothing changed hardware or software wise, and auto-updates are disabled. It was working perfectly the night before. After some testing, I found that:

- The Thunderbolt Display itself works fine on native TB1/2 Macs (tested using a 2011 and 2015 MBP).
- The M4 MBP's TB5 ports still work as normal, connected USB-C displays, my iPhone and other devices, all of which function flawlessly.
- Tried it on a Windows 11 laptop with TB4 ports, to no luck either.

Assuming that the TB3-TB2 adapter had failed, I contacted Apple Support and was shipped a warranty replacement adapter. However, the replacement behaves the exact same way.

I initially thought the replacement TB3-TB2 adapter was dead-on-arrival, but when I plugged it into a friend's 2018 MBP running Ventura, the Thunderbolt Display lit up immediately. I plugged it back into my M4 MBP and got nothing, it doesn't even show up in System Report. Diagnostics show no issues with the MBP.

At this point, I'm completely stumped. Apple is wanting to send me a second replacement TB3-TB2 adapter, but I'm doubtful that it will fix anything. Could this be a software/firmware issue on the M4 MBP instead?

TL;DR:
- Setup worked perfectly for almost a year before failing randomly one morning
- The Thunderbolt Display itself works
- The M4 MBP's TB5/USB-C ports work
- Neither my original and replacement TB3-TB2 adapters are recognised on the M4 or Windows laptop
- Replacement adapter does work on an older Intel TB3 Mac
- Diagnostics on the M4 MBP show nothing wrong

 

[Fishrrman]

I need to relate this experience before going further:

A number of years back, I had a MacBook Pro (I think it was a 2010) with firewire.
I think it had Mac OS "Lion" installed.
One day, for no apparent reason, it wouldn't connect to firewire devices any longer.
The Apple System Profiler reported "no firewire ports found".
But it HAD a physical FW port. What was going on?

Took it in under warranty. I asked if it was a motherboard problem, and the genius bar fellow said, "not necessarily". But they exchanged the motherboard anyway, and then the firewire worked again.

For a while.
Then, one day, it stopped working... again.
It was now out-of-warranty, and I wasn't going to pay for a motherboard replacement, so I just "let it be".

A few months later I was experimenting with an external drive and the new "Mountain Lion". I generally install and test a new OS version like this before I commit to a do-over on the internal drive.

Got the MBP booted up and running on the external drive, and deciided to try an external firewire drive with the Mac again.
It worked. Everything back to "normal".

I'm guessing that some software component ... maybe a kext file ... hadn't been loading previously.

Told you that to tell you this:
Could your problem be something "in software", perhaps a kext file getting "missed" during bootup? There seem to be quite a few Tbolt kext files:

Hmmm...
Reread and noticed you have TWO OS's running from the single internal SSD?
I'm thinking that has something to do with your problem, somewhere.
You might give some thought to
- picking ONE OS
- backing up that container or partition (I would recommend either CarbonCopyCloner or SuperDuper - I've never trusted time machine)
- completely "wiping" the internal drive using "erase all content and settings"
- reinstalling your data.

I know this is something you don't prefer, but...
... it is what it is.

 

[Bigwaff]

Have TBD with TB3 > TB2 adapter as well. About a year ago, the TBD started randomly going dark. Had to disconnect and reconnect the adapter for display to light up, until one day it just stopped. Discovered I could use a TB2 cable directly from the display daisy-chain TB2 port to the TB3>TB2 adapter. The TBD has been working perfectly this way since. Every now and then I'll attempt to use the built-in TB2 cable with mixed results so I've stuck with the separate TB2 cable. I guess the attached built-in TB2+Power cable is known to go flaky or fail over the years.

 

[theMarble]

Reread and noticed you have TWO OS's running from the single internal SSD?
I'm thinking that has something to do with your problem, somewhere.
You might give some thought to
- picking ONE OS
- backing up that container or partition (I would recommend either CarbonCopyCloner or SuperDuper - I've never trusted time machine)
- completely "wiping" the internal drive using "erase all content and settings"
- reinstalling your data.

The Tahoe installation was a test I did after these issues started to see if it was something to do with my Sequoia installation. It is a fresh install on a separate APFS volume, however I'll still try a new install on an external SSD to see if that helps at all.

System Profiler does show all three Thunderbolt 5 ports, and as I mentioned in my post I can hook up any other device to them without issue.

I guess the attached built-in TB2+Power cable is known to go flaky or fail over the years.

I'm leaning towards this theory as well, considering I was having some issues with USB devices connected to the display randomly disconnecting in the months leading up to now.

However, it wouldn't explain why the display worked both on its own (on TB1/2 Macs) and with the replacement TB3-TB2 adapter on a 2018 MBP. I'd have these machines open right next to each other, and plugging it into the older Macs would light up the display, but nothing on the M4 MBP.

So all that would be needed is a male-to-male TB2 cable? I'll have to see if I can find one locally.

 

[Bigwaff]

So all that would be needed is a male-to-male TB2 cable? I'll have to see if I can find one locally.

Yup. Got several off eBay couple years ago.