2018 MacBook Pro Target Display Mode Not Working

With the 10.14.1 update only installed on my MacbookPro the dual screen and the sound through the iMac speakers works perfect for me.

UpTab mini display port adapter, thunderbolt female to USBc got my CinemaView working.

Senior advisors at Apple don't know. Promised a couple articles on this but NEVER delivered.

Wanted pics of my configuration so when the UpTab arrived and external monitor was working sent them pics of the fix AND GOT NO REPLY.

So for target display mode thunderbolt provides the only working display mode solution 😉 No specifically adapter here.

source-type provided by the computer --TO-- distination-type required by the display, in at most ONE adapter.

In this case, thunderbolt-3 to thunderbolt-2 is the only thing expected to work, and many users on this thread are reporting it does not work at this writing.

Ok so I got this working today... in a round about way. I’m running a LG UltraFine 5k through the thunderbolt 3. I then wondered what would happen if I tried the iMac in target display as a third (including the laptop screen) display. Sooo I press cmd&F2 expecting the usual visual scramble that follows and sure enough... BAM, same visual crap but... it slowly, over the course of the next minute or so sorted itself out. A bit like an old tv gradually tuning into a channel. Anyway after about 2 mins max it popped up just fine and has now been working all day.

So good need is the Thunderbolt Display out on the MBP2018 can do TDM. It seems that having the UltraFine as well made it work slightly differently.

I appreciate that this isn’t the instant answer people without another monitor want as that’s the reason you’re using the iMac as a second in the first place but for those of you that have another monitor it’s worth using that a second and then trying the target on the iMac. FYI IMac is a mid 2012 27”.

Cheers!

I'm having the same issue. Called Apple support and they asked me trying different debugging techniques, did not work.

After a couple of days they said the engineers had realized it's a common issue solely for MacBook Pro 2018 model and will release a firmware update fixing this. They just don't know when the update will be released.

Update: Just spoken with Apple Support. Number of scenarios discussed. And got the following confirmed:

"It looks like you are not the only one who has problems with Target Display Mode in combination with MacBooks from 2017-2018. That is why I would like to inform you that Apple is aware of the problem and tries to solve it as soon as possible.

In the meantime, Apple asks its customers to exercise patience. As soon as the solution is available, Apple shares it with its customers via a software update."

Software update coming soon finally 🙂

nup no sound, but the update today makes my iMac work in target display mode. lucky i just plugin the sound through my studio system works via the MBP, but definitely a bug not being able to use the iMac speakers at all. same issue as you @worltravelingphotopro

I can confirm TDM does work through a duel thunderbolt drive by daisy chaining. Mount the drive on the MBP and chain to the iMac.

This is fixed!

The latest Beta has fixed the issue 🙂

I am having the same issues and have been going back and forth with support with no luck. I did reach the upper level engineers and he confirmed he saw similar behavior. They still sent new adapters and cables (was already using Apple versions) to try and that made no difference. They had me create a partition and test but it behaves the same. I tested a clean High Sierra install and Mojave as well on a partition and get the same blank screen or blinking that I get with High Sierra.

Support started by saying it was likely an accessory, but after now testing three cables and two adapters and several version of the OS I think this must be hardware or something lower level that needs to be addressed.

The most useful thing I have heard was that it seems like a bandwidth issue, something like the new machine is sending data faster than the older machines can process. Makes sense if there is a bug and the handshake on thunderbolt version isn't correct.

I keep replying to on my support case, but haven't heard anything in a week or so now.

I just contacted apple and the result is nothing, blank. They couldn't even tell if the problem is going to be fixed and when. I told them to search in google "MacBook Pro 2018 target display mode". The first result is this discussion, just to show them that we are a lots of people that have the same frustrating problem. And remember MANY IS POWER, so each one of you that are following this chat and having this problem, please right a ticket to apple or even chat them or call them, and this bug will be solved earlier!!!
Writing a feedback: Product Feedback - Apple

I just updated my Mojave to beta 4 this evening and when you connect your 2018 MacBook Pro to your iMac, type Command F2 and the screen mirrors instantly. Works great. You then can drag you open screens over to the larger display without any problems. Connected with a mid-2011 iMac 27". Great to have the second display working.

Yes. I have 2018 15" MBP with touchbar connected to mid-2011 27" iMac. Had problems until I realized my old 3rd party keyboard was not recognizing keyboard strokes CMD F2 until I went back to original keyboard. This may or may not be your issue. It's crazy that there are multiple ways for this configuration to fail, but it may help to know someone else has figured it out -- good luck!

I was planning on contacting Apple when I get a chance, I just have to find the time at work

You can asynchronously message/chat with support via the iOS app:

Apple Support on the App Store