Lenovo Yoga c940 no 3rd display out HDMI

Hi, i have a Lenovo Yoga c940. I believe is supports USBC alt mode, as i am able to connect a screen to the HDMI port by itself. I now have 2 screens connect to the displayports at 1080p, and i cannot get the same screen to connect on the hdmi.


Thank you for contacting us, I am sorry this is not working as expected and I am happy to help!

From Lenovo’s specifications there are two versions of the Yoga C940, a 14-inch and 15-inch model ( C940-14IIL and C940-14IRH ). Both of these should support USB-C DisplayPort Alternate Mode on the USB Type-C/Thunderbolt 3 ports.

Windows defaults to mirroring external displays, this can cause display detection issues, please try the following:

  1. Use the Windows keyboard shortcut: [Win]+[P] (Press and hold the Windows flag key, then tap the ‘P’ key, release both keys )
  2. From the Windows “Project” menu, select the “PC Screen Only” option to disable all connected displays
  3. Repeat steps #1 and #2, this time select the “Extend” option to set all connected displays to extended desktop mode.

I also recommend we double-check to ensure the docking station is connected to the computer using the original USB Type-C data cable provided with the docking station. USB-C cables included with other products, or sold online as “charging” cables may not support USB 3.0 data or USB-C DisplayPort Alternate Mode video data. Connecting the docking station through another device, like a USB Type-C sharing switch, USB Type-C to USB Standard-A adapter, USB Type-C cable extension, or USB Type-C hub will block the video data and disable the HDMI output port on the docking station.

The original USB Type-C data cable provided with this docking station is about 3ft/.9m in length and is black with black ends. If you are not sure if the docking station is connected with the original USB-C data cable we can gather some log files from the system to check to see if the docking station is being detected as a USB 3 device, or USB 2 device, indicating a compatible USB Type-C data cable or incompatible USB Type-C charging cable respectively.

If you would, please keep the dock connected to the computer with monitors connected to the docking station (even though one may not be working) and attach the output of our diagnostic utility PlugDebug ( http://plugable.com/support/plugdebug ) to an email to ‘support@plugable.com’ with the subject line ‘Ticket #397004 - Attention Pat’ as this will allow us to examine some log files from your system to help determine the next steps.

Please let me know if this helps, and if not we can examine the log files and go from here.

Thank you,

Plugable Technology


We’re closing this thread due to inactivity, but if you have any further questions please feel free to contact support@plugable.com and we’ll be happy to help.


Plugable Technologies