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Paper Tape
Posts: 2
Registered: ‎05-06-2019
Location: NO
Views: 208
Message 1 of 4

X1C6 external ultrawide with Thunderbolt constant disconnects


One of my users are experiencing frequent dropouts of video and power when using his Carbon X1 6th gen on a philips 3440 x 1440 ultrawide with thunderbolt, the screen is also capable of delivering power to the machine. 

When we plug in the USB-C 2 things might happen.
1. The built in screen flashes a few times then gives up, only to use the built in screen, no power is being sent to the computer.

2. It works. Screen flashes onces like it windows usualy does when you connect a external monitor and power is being delivered to the computer as well.

But even if it works it will eventualy drop out after a random period of time, might be 5 minuttes later or it might even last for 3-4 hours.

Here are the things ive tried so far.
Update the thunderbolt firmware.
Update the Intel 620 integrated graphics driver.
And i have also flashed the bios with the newest version.
I also tried on several diffrent monitors all the same model and i have also tried with a brand new X1C6 but it shows the exact same behaviour.
New USB-C cable
Reset button(pinhole) under the computer

It also worth mentioning that i tried connecting a X1C5 to the same monitors with the same connector (USB-C) and they work flawlesly.
Is there somthing wrong with the hardware on the X1C6 or is this a driver issue?

The screen is a Philips 349P (349P7FUBEB/00)

Im kind of stuck on what to do now, any sugestions and help is very much appriciated.

Community SuperMod
Community SuperMod
Posts: 4,691
Registered: ‎04-25-2008
Location: US
Views: 174
Message 2 of 4

Re: X1C6 external ultrawide with Thunderbolt constant disconnects

Hi Small-Data, and welcome to the Lenovo User Community!


I use an X1C6 with a Thunderbolt 3 monitor daily (LG 34WK95U-W 5120 x 2160). I had one Thunderbolt 3 cable go bad, and that produced similar results. I also note that you don't mention updating the Thunderbolt 3 Software, or using the Emergency Reset (button in pinhole on bottom). Give those a try.

I don't work for Lenovo. I'm a crazy volunteer!
Paper Tape
Posts: 2
Registered: ‎05-06-2019
Location: NO
Views: 169
Message 3 of 4

Re: X1C6 external ultrawide with Thunderbolt constant disconnects

I have tried with several new USB-C Cables, and i have also tried the reset button (i'll edit my post Smiley Tongue)

Just updated the Thunderbolt software you linked, will report the results tomorrow.


Paper Tape
Posts: 1
Registered: ‎09-16-2019
Location: TW
Views: 46
Message 4 of 4

Re: X1C6 external ultrawide with Thunderbolt constant disconnects

I have a very similar issue, if not the same.


My setup is a Thunderbolt 3 Dock (40AC) with power, monitor and wireless USB keyboard/mouse dongle.

Laptop is also a X1C6 with the following drivers and firmware versions:

ThinkPad Thunderbolt 3 Dock Driver V10017

Dock Firmware V1.0.0.20

Thunderbolt Software V17.4.78.500

Thunderbolt Firmware


The connectivity will intermittently drop and reconnect in what appears to be random intervals.

When it happens, it will repeatedly disconnect and reconnect for the monitor (screen flashes) as well as the power supply.

It happens on both Display Port and HDMI.

I can also hear the power circuitry seems to be switching on and off during the connect/disconnect cycles.

Once it happens, it will keep on cycling through connect/disconnect rapidly for at least 5~6 repeats.

The USB dongle for wireless keyboard/mouse sometimes will not come back at all and just stops functioning altogether.


I have now connected both the monitor and USB dongle to the laptop directly, and only use the dock for power.

Even then, the power will still go through the disconnect/connect cycles at random.

At least I am not able to figure out what triggers this issue so it appears to be random.


If anyone has fixed the issue or made any progress, please do share the information!

Right now, my expensive dock only acts as a power supply.



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