2018 MacBook Pro Target Display Mode Not Working

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.

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.

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.

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.

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 have used Target Display Mode with a 2013 iMac and a 2016 MacBook Pro via thunderbolt cable, with no problems, for two years. It is only when I tried connecting my new 2018 MacBook Pro that the problem arose, the same one everyone else is reporting. I'm fairly confident this is an issue with the new MacBook Pro

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

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.

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.

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.

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.

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!

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.