Display – LG UltraFine 5K Numbers with MacBook Pro 2017

Yesterday, everything worked well. I had my MacBook Pro (four USB-C ports and a touch bar) connected to my LG UltraFine 5K monitor (Model's official name: LG 27MD5KA – B). At the end of my work day, I turned everything off. In the morning, I restarted everything but nothing seemed to work.

I proceeded to disconnect the monitor from the MBP and this one turned on without any problem. I've tried to plug in the monitor again and the MBP's screen has turned black. Eventually, the touch bar was no longer responding. I've tried all kinds of combinations to solve the problem:

  • Turn off the MBP, unplug everything from the mains, wait a moment and reconnect everything;
  • MBP PRAM reset;
  • MBP SMC reset;
  • Tried with another MBP touch bar;

One thing works only when the LG UltraFine 5K is connected to the mains and I connect an MBP with the cover. In this case, the monitor turns on, although very weakly, I can see the Apple logo, then suddenly the logo extends horizontally on the screen and the bottom quarter of the screen is distorted (everything is very pale) . If I open the lid, only the Caps Lock appears to work (which suggests that the computer has not crashed). If I pick up the MPB, it responds without problems after a few seconds. The reconnection and the MBP screen turn black and the computer stops responding (except for the capital lock). However, I can access the computer by remote connection (SSH) and have managed to turn it off or restart from there (sudo shutdown -h now or sudo shutdown -r now).

I even downloaded the LG screen manager, but the application seems totally useless in my case (although the copyright notice seems strange, it says "Copyright 2016-2026 LG Electronics Inc." ).

Do you have any suggestions to make (apart from bringing the device for repair)?


System used:

  • MBP (13 ", 2017, 4 Thunderbolt-3 ports, Intel Core i5 3.1 GHz, 8 GB RAM, Intel Iris Plus Graphics 650 1536 MB);
  • MBP (13 ", 2017, 4 Thunderbolt-3 ports, Intel Core i7 3.5 GHz, 16 GB RAM, Intel Iris Plus Graphics 650 1536 MB);
  • Bothe MBP are installed with macOS Mojave Version 10.14.2
  • LG UltraFine 5K (aka 27MD5KA – B);