Troubleshooting: When USB-C Video Output Fails on Dell 14 Laptop
I bought a Dell laptop 'Dell 14 DC14255' and excitedly connected it to a Dell external monitor (U2723QE) with a USB-C cable.
"Huh? No display..."
Power is supplied, the monitor is detected, and USB devices (data transfer) on the monitor side are also usable, but the screen simply won't display!
The Dell 14 should have a USB-C port that supports DisplayPort 1.4.
Since it works with an HP laptop, it's unlikely that the monitor or cable is faulty.
So, after some trial and error, I managed to get it working, and I'll share the troubleshooting steps I took.
If you've found a solution or have a different experience, please feel free to comment.
The laptop featured in this article is introduced here.
Table of Contents
Conclusion
To conclude, I got it to display by changing the monitor's setting for "Display > USB-C Prioritization" from "High Data Speed" to "High Resolution".
However, the data transfer speed seems to drop to 480Mbps (equivalent to USB 2.0).
This doesn't affect me, as I only connect a webcam and mouse/keyboard dongles.
In my case, to access this monitor setting, I needed a USB-C connection. However, when connected to the Dell PC, the monitor buttons were unresponsive.
So, I changed the settings while connected to an iPhone or iPad.
Also, the above applies to Dell monitors (U2723QE), so I've summarized the settings for major manufacturers below.
| Manufacturer | Setting Location/Name | Video Priority (4 lanes) *Recommended choice |
Data Priority (2 lanes) |
|---|---|---|---|
| Dell | Display → USB-C Prioritization | High Resolution | High-Speed Data |
| Samsung | Menu → Settings → Connection → External Device Manager → USB-C Preference | High Resolution | High-Speed Data |
| EIZO | Admin Settings → Signal Format → USB-C | 4K UHD 60Hz / USB2.0 (WQHD models: WQHD 60Hz / USB2.0) |
4K UHD 30Hz / USB3.1 |
| Lenovo ThinkVision | Disable USB3 in OSD USB settings (USB Source → USB 2.0) | Select USB 2.0 | Keep USB 3.0 |
| HP | OSD → Performance Mode | Disable Performance | Enable Performance |
| LG | Many models do not have this setting | Automatically operates in USB 2.0 mode when connected via USB-C (= effectively fixed 4 lanes) | — |
If you can't find these settings on your monitor, it's highly likely that video output via USB-C cable is not possible, but please try the suggestions in the next section just in case.
If you've found a solution or have a different experience, please feel free to comment.
What I Tried
① Resetting or Updating Graphics Drivers
Pressing Win + Ctrl + Shift + B simultaneously reloads the graphics driver. (The screen flickers for a moment.)
I tried this both with the monitor connected and disconnected to see if it improved, but it didn't work.
In the case of Dell, an update for the AMD graphics driver was found via "Dell SupportAssist" software, so I updated it, but it didn't work.
It's a basic step, but also make sure that Win + P is pressed and it's set to something other than 'PC screen only'.
② Replacing the USB-C Cable
The USB-C cable I was initially using was this one.
![Elecom USB-C Thunderbolt 5 Cable 1m 240W High-Speed Data Transfer USB PD Compatible 8K/60Hz Max 120Gbps Slim Cable [Intel Certified] MacBook Pro/Mac Mini (2024 Model) Compatible TBT5-10BK](https://m.media-amazon.com/images/I/61i+AGmwQhL._AC_SY606_.jpg)
Elecom USB-C Thunderbolt 5 Cable 1m 240W High-Speed Data Transfer USB PD Compatible 8K/60Hz Max 120Gbps Slim Cable [Intel Certified] MacBook Pro/Mac Mini (2024 Model) Compatible TBT5-10BK
It's a high-spec Thunderbolt 5 cable, but Dell laptops are not Thunderbolt, so
So I purchased a USB-C cable that is not Thunderbolt, but purely "DisplayPort Alt Mode" only.
ADTEC USB 3.2 Gen2 1.0m eMarker Equipped USB Type-C Cable PD 100W 5A Compatible eMarker Equipped 10Gbps High-Speed Data Transfer 4K 60Hz Video Output DisplayPort Alt Mode DP-ALT Type-C Smartphone Tablet Laptop Charging High-Speed Charging Fast Charging 1m Black APC-V1010CC-4KU3G2-B
However, the result was the same.
But at this point, there might also be compatibility issues, so if you can't find a solution, you might want to try this.
③ Checking if iPhone Displays (Isolating the Cause)
First of all, checking whether the USB-C cable and monitor support DisplayPort is a way to isolate the cause.
In my case, I was sure because it worked with an HP laptop,
but I recommend trying to connect a DisplayPort-compatible device (such as an iPhone (15 or later) or iPad) to see if it can output video.
If compatible, it will display like this.
That concludes the troubleshooting guide for when a Dell laptop cannot output video to an external monitor via USB-C cable's DisplayPort Alt Mode.
If you've found a solution or have a different experience, please feel free to comment.
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