LG 23” 4K UltraFine and 16” MBP not working properly

[SBruv]

Hi all,

Just wondering if anyone else is having peripheral connectivity issues with the 4K UltraFine and the 16” MBP.

The display itself works fine, but after connecting the MBP, none of the USB or Thunderbolt peripherals plugged into the back of the display are recognised. The only way to get everything to appear as it should is to restart the MBP, whereupon everything works as expected. Kind of annoying having to restart every time, rather than just plug it in and get busy.

It’s not a power supply issue, because it happens whether the MBP is also powered via its own charger or not; and hard disks, MIDI controllers, etc, with their own power supplies also don’t connect without a restart.

I’m assuming it’s an issue with the 16” MBP, but actually, I guess it could just be a Catalina thing.

Can anyone with the same monitor and Mac confirm/deny?

 

[poorcody]

I have the 16" and a 5K Ultrafine -- not seeing this problem. USB peripherals work as expected.

Have you tried disconnecting the devices one-by-one to see if one of them is causing a problem?

 

[SBruv]

I have the 16" and a 5K Ultrafine -- not seeing this problem. USB peripherals work as expected.

Have you tried disconnecting the devices one-by-one to see if one of them is causing a problem?

Yeah, doesn't matter if I just have a single device attached, it's still the same.

 

[pshifrin]

I have the LG 4k Ultrafine, same as you and I'm testing a 16 inch. I hadn't yet plugged it into the 4k as I've been working all day on my 15inch and guess what, it's not working correctly for me either!

It is recognized but not charging. I moved the cable around to other ports and sometimes it charges and sometimes not. The ports on the back (I have a Belkin ethernet adaptor always plugged in) DID work however.

Using my 15 inch that does work correctly, I ran LG screen manager and there are no firmware updates available for the monitor.

It could be the cable, but I don't have another one to try and it does work perfectly with the 15.

 

[SBruv]

I have the LG 4k Ultrafine, same as you and I'm testing a 16 inch. I hadn't yet plugged it into the 4k as I've been working all day on my 15inch and guess what, it's not working correctly for me either!

It is recognized but not charging. I moved the cable around to other ports and sometimes it charges and sometimes not. The ports on the back (I have a Belkin ethernet adaptor always plugged in) DID work however.

Using my 15 inch that does work correctly, I ran LG screen manager and there are no firmware updates available for the monitor.

It could be the cable, but I don't have another one to try and it does work perfectly with the 15.

Have you tried restarting the Mac while it's connected? I bet that'll make it work. Mine also didn't charge the first time I tried it with the 4K – didn't realise it wasn't charging until it drained and turned off! That hasn't happened since, but now I've got no USB or TB connectivity.

Also, your ethernet adaptor presumably doesn't require power. I wonder if that's why it's working. Do you have a hard drive you can try? Unplug the MBP from the monitor, plug in a hard drive, reconnect the MBP and see what happens…

And I've just tried the monitor with my Mac mini, also running Catalina, and it works perfectly in every sense, so it clearly is an issue specific to the 16".

Still, at least LG's support is absolutely top notch, so no doubt a fix will quickly… Oh, wait, no… :..(

 

[pshifrin]

Have you tried restarting the Mac while it's connected? I bet that'll make it work. Mine also didn't charge the first time I tried it with the 4K – didn't realise it wasn't charging until it drained and turned off! That hasn't happened since, but now I've got no USB or TB connectivity.

Also, your ethernet adaptor presumably doesn't require power. I wonder if that's why it's working. Do you have a hard drive you can try? Unplug the MBP from the monitor, plug in a hard drive, reconnect the MBP and see what happens…

And I've just tried the monitor with my Mac mini, also running Catalina, and it works perfectly in every sense, so it clearly is an issue specific to the 16".

Still, at least LG's support is absolutely top notch, so no doubt a fix will quickly… Oh, wait, no… :..(

I just tried it with an orange Lacie 4tb USB-C hard drive and it did work correctly each time with a few plugs and unplugs. I'm returning the 16 for a variety of reasons, add this to the list

 

[SBruv]

I just tried it with an orange Lacie 4tb USB-C hard drive and it did work correctly each time with a few plugs and unplugs. I'm returning the 16 for a variety of reasons, add this to the list

Ah, okay, so it didn't just work first time, then, no? Glad to hear it's not just me, but not glad that it's happening at all, obvs.

 

[pshifrin]

Ah, okay, so it didn't just work first time, then, no? Glad to hear it's not just me, but not glad that it's happening at all, obvs.

Sorry, I wasn't clear in what I wrote. The drive was recognized the first and every subsequent time I plugged in.

Note, this was after a reboot. I actually had started the internet restore process to wipe the Mac to prep it for a return on my way home tonight when I saw your request to check it with a HD so I stopped that and tried what you asked.

It's a shame because I do like a lot about the 16 inch but I can wait a few months. I don't need to pass down my 15 inch to another employee until the spring. Hopefully by then any production run issues (screens) and software issues with Catalina will be worked out.

 

[SBruv]

Sorry, I wasn't clear in what I wrote. The drive was recognized the first and every subsequent time I plugged in.

Note, this was after a reboot. I actually had started the internet restore process to wipe the Mac to prep it for a return on my way home tonight when I saw your request to check it with a HD so I stopped that and tried what you asked.

It's a shame because I do like a lot about the 16 inch but I can wait a few months. I don't need to pass down my 15 inch to another employee until the spring. Hopefully by then any production run issues (screens) and software issues with Catalina will be worked out.

Ah, right. Thank you for holding up your restore to try that.

When you say it was after a reboot, do you mean you rebooted while the MBP was connected to the monitor, or your rebooted, then connected to the monitor? If the former, yes that works for me too; if the latter, then that's not the behaviour I get – I have to reboot while connected for all connected peripherals to spring to life.

And what's wrong with your screen?

 

[nudoru]

I have them both and I'm not having any issues with the combination. Everything is working just like I'd expect it to.

 

[SBruv]

I have them both and I'm not having any issues with the combination. Everything is working just like I'd expect it to.

Interesting. What do you have plugged into the monitor?

 

[pshifrin]

Ah, right. Thank you for holding up your restore to try that.

When you say it was after a reboot, do you mean you rebooted while the MBP was connected to the monitor, or your rebooted, then connected to the monitor? If the former, yes that works for me too; if the latter, then that's not the behaviour I get – I have to reboot while connected for all connected peripherals to spring to life.

And what's wrong with your screen?

meaning because I stopped the internet restore, it had just started booting with the globe icon, and I then I booted it normally, it was “rebooted” since the first time I plugged it into the LG.

screen was unusually dim and yellow on my first one, this one was an exchange.

its already been returned and the apple store employee asked why and handed me his device to let me type in the explanation, which I tried to give in detail.

 

[jukeboxaddict]

I also have both and the combo seems to work okay — though this display can be awfully finicky. Sometimes the screen just won't light back up when I unplug / plug back into the MacBook Pro until after a restart. But that was true before I got the 16.

Also keep in mind that the UltraFine 4K's Thunderbolt port puts out a max of 85W, so it can't juice the MacBook Pro at full speed. Does anyone know if this impacts performance on the machine?

 

[SBruv]

I actually discovered – after a great deal of exploration – that the whole problem was caused by an old LaunchAgent for the Arturia AudioFuse audio interface. Deleting that fixed it entirely.

 

[G5isAlive]

I actually discovered – after a great deal of exploration – that the whole problem was caused by an old LaunchAgent for the Arturia AudioFuse audio interface. Deleting that fixed it entirely.

Glad that you figured out the problem, could you explain how or what led you to try that? I suspect I get caught up in similar things but dont have the expertise too diagnose like you do.

 

[SBruv]

Glad that you figured out the problem, could you explain how or what led you to try that? I suspect I get caught up in similar things but dont have the expertise too diagnose like you do.

Well, it was actually discovering that my other USB hubs also weren't working consistently with the 16" MBP (despite working perfectly with my 15") that made me realise it had to be a problem with the Mac rather than with the monitor. Then, to establish whether it was down to the hardware or something in macOS, I booted into Safe Mode – voila, all hubs and the monitor worked perfectly.

This suggested that it had to be either a third-party KEXT, LaunchDaemon or LaunchAgent that was causing the issue, not the Mac itself, as these aren't loaded in Safe Mode. So I removed all third-party KEXTS and restarted the Mac – problem still occurred, so I put them all back. Removed all LaunchDaemons and restarted – problem still occurred, so I put them all back. Removed all LaunchAgents and the problem didn't occur – the monitor and all hubs worked as they should. Then it was just a case of replacing LaunchAgents in small groups to find the one that was the root of the problem. I guess Arturia's LaunchAgent just needs updating to work with the USB chipset in the 16".

(Emphasis very much on 'third party', btw – don't go moving Apple's own KEXTS or LaunchAgents/Daemons around!)

 

[impulse462]

Unfortunately I get this on my LG ultrafine 5K also. when i connect my computer to any other 3rd party display it works fine, but connecting to the 5k, there is always some lag between connecting it and the display getting turned "on" (more so than a lot of other displays ive tried) and occasionally (like 10% of the time) the display just wont work and i have to open my laptop and then close it again and connect it. really quite frustrating for a >1k display