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LG UltraFine 5K monitor - external devices not detected

Hi,

Few days ago I finally received my new LG UltraFine 5K display. I also purchased the new MacBook Pro (15 inch) with GPU upgrade, i7 upgrade and 1TB flash storage.

Connecting the LG display to the MacBook is working fine. However when I disconnect the LG display by unplugging the USB-C cable and subsequently reconnect the USB-C cable in the MacBook, the external devices in the other USB-C ports of the LG monitor are not detected.

I have a USB-C to USB adapter with a lightning cable for my iPhone plugged in & a Belkin USB-C to Ethernet adapter connected to my router. These two cables are not detected after unplugging and reconnecting the MacBook with the display.

I need to unplug both cables on the back of the display and plug them back in in order to have the monitor detect them.

Is this a known issue?

Posted on Dec 29, 2016 6:35 AM

40 replies

tedder42

Level 1

8 points

Oct 29, 2017 8:26 AM in response to Nick Brook

Still a problem, of course. Basically after plugging the laptop into the USB-C connection to the monitor, I have to unplug/replug any other USB connections on the back of the LG for them to be recognized.

Dec 1, 2017 6:58 AM in response to JoelCraenhals

I also have this problem with the LG 27UD88-W (4k USB-C) monitor attached to my MBP-15 late 2016 TB.

My USB-A wired mouse is connected to the monitor directly and sometimes works, sometimes not. I rarely also have similar problems when connecting the mouse to a normal USB-C port via an adapter directly to the MacBook. I then have to change the port. This makes me thinking it is Apple, not LG, but in general, I know these USB issues are hard to debug.

The Monitor has the latest Firmware, my MacBook Pro is still on Sierra.

Dec 6, 2017 12:21 PM in response to JoelCraenhals

I found a solution that worked for me!

Download the LG Screen Manager from their website under software, firmware & drivers: http://www.lg.com/us/support-product/lg-27MD5KA-B

Open the app and Install the latest software update while the monitor is connected. After it completes unplug all USB devices devices and the monitor, then plug them in again.

MoonJ.

Community Specialist

Dec 29, 2016 6:44 PM in response to JoelCraenhals

Hi there JoelCraenhals,

It sounds like your USB-C devices which are connected to the LG monitor aren't detected when you unplug it and connect it again. I would suggest resetting the NVRAM and maybe even the SMC if that doesn't resolve the issue:

How to reset NVRAM on your Mac

Reset the System Management Controller (SMC) on your Mac

Thank you for using Apple Support Communities, let us know how that goes!

Dec 29, 2016 7:00 PM in response to MoonJ.

Thanks for replying.

What I did: I unplugged the LG monitor. Shut down the MacBook Pro and reset the NVRAM with Command+Option+P+R. When the MacBook Pro was completely rebooted, I plugged the monitor back in, but the devices (like iPhone and Belkin Ethernet adapter) where not detected. Unplugging the monitor one more time and connecting it again solved it and now the devices are detected, but had to unplug and reconnect the monitor. Is it a MacBook issue or more like a LG issue?

A question related to resetting the NVRAM: do I leave the monitor connected while shutting down and resetting the NVRAM?

Going to reset the SMC now on my Mac.

Dec 29, 2016 7:13 PM in response to JoelCraenhals

The issue seems to be fixed without having reset the SMC. I just did an extra reboot and now when I unplug the LG monitor, the iPhone connected to the monitor still has power and when I reconnect the monitor all devices are detected on the MacBook Pro.

Issue resolved! Thanks a lot!

sterling r

Community Specialist

Dec 30, 2016 8:18 AM in response to JoelCraenhals

Hey there Joel! Thanks for the update, it's good to know you're good to go!

Take care, and have a wonderful new year!

Jan 13, 2017 8:06 AM in response to ozziepeeps1982

I also have this issue, and have reset the NVRAM and SMC. Seems like a firmware bug in the display/MBP.

JudahDE

Level 1

13 points

Jan 25, 2017 2:17 PM in response to Nick Brook

It is an issue... I have it and have been working towards a resolution. It's annoying but not critical. Should be fixed soon.

logicito

Level 1

46 points

Jan 25, 2017 2:45 PM in response to JudahDE

What kind of resolution?

Feb 8, 2017 5:33 PM in response to Chris Messineo

I have the same issue, being on a MacBook Pro 13Inch touchbar.

Apple please advise when can we expect a solution/fix for this issue, this is a topic now for more then six weeks.

Mar 21, 2017 10:57 AM in response to jackofsometrade

I am having the same issue - LG thinks its related to the shielding - I don't believe that is true. They are not supporting their defective monitors properly.

ardias

Level 1

11 points

May 3, 2017 2:10 PM in response to McMorrisDesigns

You are correct but even more seriously is that the issue occurs with the latest 15" MBP and the LG 5k - unacceptable!

ardias

Level 1

11 points

May 17, 2017 11:00 AM in response to JoelCraenhals

10.12.5 did NOT fix the Ethernet (cable unplugged) bug. 😟

Jul 4, 2017 12:25 AM in response to arthurfromrotterdam

I concur with Arthur. Please try and re-open the support thread as the issues seems far from being solved.

LG UltraFine 5K monitor - external devices not detected