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2018 MacBook Pro Target Display Mode Not Working

Has anyone successfully used Target Display Mode with the new 2018 15" MacBook Pro? We just purchased one last week, and I am trying to use a late 2013 27" iMac as a second monitor via Target Display Mode.


When I hit command-F2 it does try to switch over, however the screen either a) remains black b) shows my screen but blinks every other second c) shows the screen but it's static-like and has crazy zig-zag colors across the background and flashes and such.


I have done all the recommended trouble shooting steps per the knowledge base article and am wondering if this is a problem with the new MacBook Pros. It is very frustrating to not be able to work on my brand new computer; I need the larger monitor for graphic design.


Both have latest versions of High Sierra. I have tried two different Thunderbolt 2 - USB-C adaptors. I have tried two different Thunderbolt 2 cables. One I have used for four years so I know it works. I have reversed the cables and tried all the different Thunderbolt ports on both machines. I connected them using Target Disk Mode to transfer my data and that worked.


I reset the SMC and zapped the PRAM. I booted in safe mode on both machines and then restarted. I have spent a good bit of time on this, but since this is a work machine I can't keep wasting time on it as I need to actually get work done, which unfortunately means still using the older iMac.


Any other thoughts?

MacBook Pro (15-inch, 2018)

Posted on Aug 2, 2018 7:53 AM

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224 replies

Aug 21, 2018 7:17 AM in response to sforner405

Thunderbolt 3 to Thunderbolt 2 Adapter

Maybe this one works.

No, no, no ...


Those ThunderBolt 3 to 2 adapters do not present ANY directly-usable display interfaces.


To connect to a Mini-DisplayPort display, you must use an adapter specifically for the conversion you need, and it must be complete in ONE adapter.

So you must have something that says "ThunderBolt-3" on the computer-end, and "Mini DisplayPort" or exactly what you need on the display end.


"Stacking" display adapters is seldom successful.


But this is not the main topic of this thread, it is a side issue.

Aug 21, 2018 7:24 AM in response to RustyBensh

But UpTab is a Mini Display Port Adapter. Would not work for IMAC Target Display Mode, because it needs a thunderbolt connection.


Grant Bennet-Alder wrote:


Thunderbolt 3 to Thunderbolt 2 Adapter

Maybe this one works.

No, no, no ...


Those ThunderBolt 3 to 2 adapters do not present ANY directly-usable display interfaces.


To connect to a Mini-DisplayPort display, you must use an adapter specifically for the conversion you need, and it must be complete in ONE adapter.

...


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

Aug 21, 2018 7:46 AM in response to sforner405

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.

Aug 23, 2018 3:44 PM in response to Pennock

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.

Aug 28, 2018 4:10 PM in response to Pennock

Hey community, I have the exact same problem. New MacBook Pro 15" i9 and I try to connect my Late 2013 27" iMac. Changed adapters and cables already and had a meeting at the Genius Bar today. The guy was very nice and tried everything. It worked perfectly with their external monitor. Unfortunately they didn't have an iMac available for a test. He asked me, that he will open a case with Apple support..... Hopefully someone will figure it out. After spending 4,300$ for my new MacBook I don't want to spent another $1,600 for a new monitor... Any help is much appreciated. Thanks all of you. Best CW

Aug 29, 2018 7:36 AM in response to Maverickos0815

Maverickos0815 - I would make sure you open your own ticket as well, I wouldn't rely on the Apple Genius to do so. Even if they do open one too, the more tickets opened the better!



It doesn't sound like anyone has been given any real answers yet, or that Apple has acknowledged this as a universal problem and just keeps treating it like an individual problem by wanting us to test cables and partitions and things which we have all seen doesn't work.


My MBP is at work, I'm hoping to get a quiet moment in the office to call again and push the issue some more. Everyone just keep calling or sending chat messages to Apple support.


I had also tried reaching out to some Apple news sites but I didn't get any response. If others did the same maybe one of them would pick up the story and help put some pressure on Apple.

Aug 31, 2018 1:18 AM in response to Pennock

I'm also experiencing this issue. I have access to several iMacs at work, and three thunderbolt cables. All iMacs are capable of Target Display Mode and work as an external monitor if I connect them to a 2016 MacBook Pro. They *all* fail to work with my 2018 model.


The latest supplemental update to High Sierra doesn't address this issue. I filed a Radar (43929442) and contacted Apple's customer service. They asked me to update the OS on both devices, to use different cables (if possible), and other things that seem like the "list of things to try". After we exhausted the list I was asked to take my devices to an Apple Store (or authorised repair center)... which I haven't done because I found this thread and have determined that this probably isn't a problem with my MBP.

Aug 31, 2018 5:55 AM in response to pg@cfit

pg@cfit - If you have the time and are able to take your machines to a store for them to look at it, it may be worthwhile. Maybe it would help prove that this is a problem with the new laptops and therefore get Apple to fix it. So far they will not acknowledge it as a problem and just keep putting us all through the same troubleshooting steps that do not work. You'd think someone in support would have consolidated all our reports by now!


There are around 100 people just on this one thread that clicked 'I have this question too' which means there are many more out there with this issue.

Aug 31, 2018 10:13 AM in response to chapimex_3

Thanks to your post, I now have my 2018 MacBook Pro working with Target Display Mode through a CalDigit TS3+! I had the exact same problem as everyone else (flickering and shut off using Target Display Mode to iMac through the Thunderbolt 3 probs on the MBP) but it is working solidly now with 2 monitors connected through a CalDigit TS3+. I have a Dell 30" monitor using the DVI port of the CalDigit, The iMac is connected to the Thunderbolt 3 port on the CalDigit using an Apple Thunderbolt 3 to 2 adapter and Target Display Mode is engaged. I wanted TDM to work via a separate MBP connection because I need the Apple adapter to connect to my Thunderbolt 2 RAID. At least for now I have a dual monitor setup.

Aug 31, 2018 11:18 AM in response to JeffQ6

Glad you got your set up worked out! That being said it would be ridiculous for the rest of us to have to buy a thunderbolt dock in order for TDM to work properly, not after spending so much on these new machines. I certainly don't want to have to buy a new monitor and have may iMac go to waste - this is on Apple to figure out, at the very least it would be nice to get an official response.

Aug 31, 2018 2:08 PM in response to Pennock

Another workaround! Just for fun, I tried daisy chaining from the Apple Thunderbolt 3 to 2 Adaptor through my Thunderbolt 2 RAID (Rockstor-4disk) up to the iMac Thunderbolt input. Thunderbolt Display Mode worked when I entered command F2! So you don't really need an expensive Thunderbolt All in one adapter (I'm using the CalDigit TB3+) to daisy chain through as it looks like you can daisy chain through anything and get it working. It's as if the daisy chain may slow or filter the "glitch" that is causing the problem. Someone mentioned it could be the new 2018 MacBook Pros Thunderbolt 3 controller may be too fast and in essence daisy chaining slows it down. I discovered this because I wanted to use my Thunderbolt 2 RAID AND my iMac in Target Display Mode at the same time (without having to buy another Thunderbolt 3 to 2 adapter) and found it actually worked. I'm using a late 2011 27" iMac running Mac OS X 10.13.6. One caveat is that you have to turn off the iMac and restart the MacBook Pro to get it to recognize the Thunderbolt 2 RAID before engaging Target Display Mode after the iMac restart. Another problem with this set up is that the iMac mounts the RAID when you disengage Target Display Mode. Hope this info helps someone.

Sep 3, 2018 9:52 AM in response to Pennock

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!

Sep 4, 2018 1:17 AM in response to Pennock

The report in Radar has been marked as "duplicated" and "open", so its seems there's some engineer at Apple working on this. Hopefully we'll get a fix sooner rather than later.


Pennock: I will take it to the Apple Store... it's just a matter of getting the appointment on a weekend... which has proven difficult.

2018 MacBook Pro Target Display Mode Not Working

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