Target Display Mode: Flickering Screen

I would make sure all of your connections are tight and try resetting the SMC How to reset the System Management Controller (SMC) on your Mac - Apple Support and NVRAM Reset NVRAM or PRAM on your Mac - Apple Support on both computers.

This is a widespread issue with the new 2018 models, check out here: https://discussions.apple.com/thread/8485517

No answer from Apple yet but make sure to notify them of the issue and talk to a senior engineer..I am waiting for a response from one as well, but they should hopefully address this soon if this is a software or hardware related issue

I have the exact same problem. So frustrating 😠. The adapter I have (USB-C to Thunderbolt 2) is the one sold by Apple. Target display mode worked fine from with my 2015 Macbook Pro. So the problem is definitely either with the adapter or with the 2018 Macbook Pro's. Because so many of us are having the problem, my guess is that it's with the computer itself and (not the iMac or the adapter).

Something of note: I have a belkin hub, and the idea popped in my head. What if I connect both my iMAC and my 2018 MacBook Pro to the hub, maybe Target Display Mode will work? I couldn't find the darn power cable to the hub, but after about an hour of searching I found it. The suspense was killing me, because I really need it and want it to work. Good news and bad news. The good news is, target display mode works just fine. The bad news, it only works for a few minutes before it starts to flicker. But, having both computers connected to the hub delays the flickering, just a tad bit.

This exact problem happened with me. My MacBook Pro is 2 days old. Bought thunderbolt 2 cable and thunderbolt3 adapter at the apple store. Tried using my mid 2011 iMac in target display mode and it squiggles, flashes off and on, and goes black. I tried the new MacBook update offered today and still having the same problem. It's a bummer because I went the laptop route specifically because of Target display mode. Now I'm thinking I should have gotten an iMac.... my MacBook Pro is an i9 processer, 32GB of ram, Radeon Pro 560X 4096 MB, Intel UHD Graphics 630 1536 MB.

Exact same issue here ...

I got my new macbook pro yesterday and could confirm the exact same issue. My 2011 iMac was working fine as a target display when paired with my old macbook pro(2013) but now with the new macbook pro the screen flickering is happening.

From various research, this is a clearly new macbook pro(2018)'s general issue that Apple must solve asap.

I wonder if there is even a single instance where Macbook pro(2018) is paired with old iMac(as a Target display)? I'm quite doubt about it...

I have the same problem too. Just bought my MacBook Pro 2018 model yesterday and I am using iMac 21.5 inch late-2013. Both are using OS Mojave. All the thunderbolt connectors are apple’s ones.

I tried everything already, should I try to do something also with the new MacBook?

Why, apple? I so wanted to connect my MacBook to my old iMac. How can I write direct to apple or contact them, if I bought my MacBook in an apple authorized reseller store?

Sorry to say, but there is no fix for this so far. I called Apple. I talked with multiple people. They talked to their engineers and got back to me. There is no known do for this. Mohave doesn’t fix it. They know about it but haven’t come up with a solution yet. Very frustrating. So now I have to go buy another monitor on top of a $4000 laptop.

Reporting same problem while my 2018 MacBook Pro is paired with Late 2013 iMac.

Screens flicker when connecting in Target Display mode using Apple's Thunderbolt cable and Apple's Thunderbolt-USB-C adaptor.

iMac works just fine in Target Display mode when connected with a 2017 MacBook Pro.

Please reply if there is any solution received from Apple.

There is no solution yet. I have an open ticket with Apple support on this and the support guy confirmed the issue had been reported back to Apple engineering where the fix was being worked on. However still there is no ETA yet.

I would recommend anyone with the same issue to open a support ticket with Apple, that would be the only way we could do at that stage.

Just for now guys, I think that sharemouse is very nice option to control both computers with the same mouse and keyboard. Though, with sharemouse we cannot move windows from screen to screen as we could do with target display mode 😕

I have the exact same issue and am currently on the phone with Apple support to see if they have found a solution yet.

I am opening a case so that any resolution, once determined, will be directed my way.

Ok good news and bad news.

The good news are that now TDM works for my 2018 MacBook Pro and my 2013 iMac.

The bad news are that my iMac goes black after stoping the TDM (by pressing command + F2 again). The only thing that returns the iMac back is disconnecting the power cord and connecting it again.

Does anyone have an idea why???

Okay! So it appears that Mojave 14.1 has fixed the issue. I am now happily using my 2018 MacBook Pro with my 2011 27" iMac as an external monitor. Make sure to update all the way to 14.1, as 14.0 does not fix the issue. Thank you apple for addressing this! BTW, you do not need to have Mojave on the iMac you are using, I have high Sierra on that one, as it is the most recent system software that that hardware allows.