External monitor gets "No Signal" from DisplayPort with new MBP 15"

On my old monitor Dell U3014, I needed to go settings of the monitor (not the laptop) and turn on the DisplayPort 1.2 support which is for some reason disabled by default. To make things worse, the local menu (and not just the input source) on this monitor becomes available only after some valid signal is already coming. Connect some other video source temporarily to it.

My mac is MacBook Pro (15-inch, 2017), OS 10.13.3 (17D102), cable Delock 85256 USB C. The display is Dell U3014, it worked fine with various computers for many years and still does.

HDMI to USB C adapter works with this monitor out of box but for some reason produces really low quality image (something wrong with colours).

Summarising, DisplayPort 1.2 must be supported by the cable and monitor, and also activated on the monitor side.

Displays attached to your Mac require that the display respond to a query sent from the Mac at certain times. The query is essentially, "what is your name, and what are your capabilities?" One of the reasons it is done this way is to avoid sending a signal that might damage your display.

Some displays, especially TV set displays, are internally set to "scan" all their ports looking for one with a signal. If the display is not paying attention to which port it should be listening to, and misses the query and does not respond, it stays dark. So if your display has a setting for which port is preferred, or which port is used to connect to a computer, that is what the display should be set for.

The query is sent:

• at Startup

• at wake from sleep

• At insertion of the Mac-end of the display cable, provided everything on that cable is ready-to-go

• on use of Option-(Detect Displays) button in Displays Preferences

If you can see (on your Internal display) to click option-(Detect Displays), you should also look to see if the NAME of the display is showing:

About This Mac > (System Report) > Graphics&Displays

name not showing means the display did not answer the query.

Occasionally, an inexpensive adapter does not carry the EDID data side channel through to the display and back. Then it will not work properly with a Mac.

Hi there! Would you mind saying the final outcome of your issue?

I recently purchased a late 2017 MBP for work and am having the same issue. Only difference here is I'm using a straight USB-C to DisplayPort cable (no adapters in between). I'm also on an ASUS monitor, but a different model (PG279Q).

I'm actually on my second cable as I returned the original one I purchased thinking it was defective. I returned that one and bought one that was a different brand. Both had solid reviews and have confirmed to work on these model MBPs. For that reason, I'm ruling out that this is an issue with the cable(s) themselves (what are the odds they're both defective). FWIW, here's the cable I'm using now: Amazon.com: USB C to DisplayPort Cable (4K@60Hz), uni Thunderbolt 3 to DisplayPort Cable for MacBook Pro 2017/2016, Dell…

Also worth noting, the display shows up just fine (proper model number and resolution) under About this Mac > Displays as mentioned by another user.

Any guidance on this would be greatly appreciated.

Thank you!

- Daniel

Hello there,

I actually have the same issue. Also tried several cables/adaptors and apparently something is wrong with Apple's soft/hardware here. No matter what adaptor I use, at some point the external monitor stops getting a signal form my MBP (being recognized by the system: I can see it in a display list, the system thinks everything is ok). The only thing that helps me is restarting the laptop (sometimes I need to reload it twice though).

P.S. I have never had an issue with those displays before with my MBP 2012 Retina, it started with MBP 2017 so it seems that something is broken with that thunderbolt 3.

Hi Krevega!

I wanted to share this with you and future visitors how I solved my issue: using a different cable. It turns out the quality of the cables on the market are hit or miss.

Here's the one I'm currently using for over a month now with no issues at all:

https://www.amazon.com/gp/product/B01EXKDRAC

I hope this helps!

Delock 85256 USB C to DP does not work. It is a good quality 4K cable, and also far from cheap. It is DisplayPort 1.2, should this be a problem? HDMI works with the same monitor but the image quality is pretty bad for some reason.

The Graphic/Displays in system report shows only "Intel built-in graphics" and "PCI Express Radeon graphic card". It does not show any external monitors present. The monitor somewhat senses a laptop (does not complain "cable unplugged), but there is no image. "Displays" setting only shows internal display. I cannot find "Detect displays" anywhere. I tried to plug-unplug cables multiple times, also tried different ports.

My mac is MacBook Pro (15-inch, 2017), OS 10.13.3 (17D102). The display is Dell U3014, it worked fine with various computers for many years and still does.

While it is ok Apple supports only latest versions of some cables, they really should specify these versions rather than making users to buy and probe the random stuff. It is not just about cheap and expensive cables, I have paid $50 for mine.

what adapter?

There is a lot more information you can collect. See my post from about the same time as yours.

Is anything seen at:

About This Mac > (System Report) > Graphics&Displays ??

does that change if you click Option-(Detect displays) and select the report again?