2018 MacBook Pro Target Display Mode Not Working

Update: I returned my MacBook Pro 2018 15" after encountering a number of different problems. I bought the iMac Pro and target display works beautifully!

I would return your MacBook Pro 2018s and wait for Apple to get it together.

I'm having the same issue, 2012 27" iMac connected to new 2018 MBP 15". I purchased the Thunderbolt 3 to Thunderbolt 2 adapter ($50). This works flawlessly with my 2013 MBP but not so much on the new machine.

My iMac will blink for about 20 seconds then gets all weird grainy while blinking and making a horrible noise then the screen goes black.

All my cables are thunderbolt and have triple checked the compatibility of everything. When I hook up the older MBP

it just works. Come on Apple $2500 on a new machine and it just does not work 100%...

I spent all afternoon trying to get this working and I'm sure this affects a bunch of your customers as they require multiple monitors to do their work. Many of which have and slightly older iMac that works great as a monitor.

It seems that for now the target display mode is not working on the new MBPs, however there was a reference to an expensive hub that would allow the target display mode to work - what is that hub? There were also references on possibly daisy chaining the computer you were using TDM on to the other monitor so it could be used again does anyone have directions on how to do that?

Thank you

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.

TayDC wrote:

Now that is weird! Apple discontinued TDM on iMacs post 2014, so the fact that it works on the iMac Pro is certainly a surprise

The iMac Pro is using a 2013 iMac as an extra display. The 2013 iMac is in Target Display Mode, not the iMac Pro.

I've got the same issues & escalated @apple as well.

One workaround: If I connect MBP and iMac through a 1st Gen Belkin Thunderbolt dock, Target Display Mode works flawlessly.

Apple Support is trying to figure out what the dock is doing differently to make it work...

Cheers, c

Could you please let me know the product information of that Belkin thunderbolt dock you were using?

I tried Apple thunderbolt 3 to thunderbolt 2 adapter, it only worked on MacBook Pro 2016 not 2018.

Thanks!

During my preparations for the upcoming phone call with Apple Support I've tried to connect the 2018 MBP with my Late 2013 iMac 27". Guess what... the connections is working! However it's not stable and the display blinks regularly for 5 seconds. Waiting for the call now. Give you an update later.

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 🙂

It's this dock: https://www.macworld.com/article/2037026/review-belkins-thunderbolt-express-dock -lets-you-get-plugged-in-easily.html

The USB-C / TB3 to TB-Adapter works fine for connecting the 2018 MBP to the dock.

The trick seems to be daisy chaining the MBP and iMac through the dock (or through a Thunderbolt Harddrive, as another user reported) instead of connecting them directly.

I have the same problem. I've logged a support ticket with Apple.

I have a 2018 MBP.

iMac Mid 2011

Both are running High Sierra 10.13.6

Thunderbolt 2 cable

USB-C to Thunderbolt 2 adaptor

All genuine Apple parts.

The cables work perfectly for data transfer in Target Disk mode.

The cables (excluding adaptor) work perfectly from an old MBP.

I've tried resetting the NVRAM and SMC. Neither work.

Symptoms: Screen flashes on iMac, display preferences on new MBP show it is connected, but then disconnects after a short while. You can see the mouse move on the iMac and the wallpaper of the MBP displayed on iMac in between flashes. Then iMac screen goes black.

Following this to find the solution....

hey guys, just want to confirm that I used Belkin Thunderbolt 2 Express F4U085TT to connect my MacBook Pro 2018 with an iMac 2013. The iMac can be used as a target display. No flickering, no dark display. It just worked flawlessly.

Basically, you need a Thunderbolt 3 to Thunderbolt 2 adapter and the Thunderbolt 2 cable that comes with the dock to connect your MacBook Pro to the dock. then need another thunderbolt 2 cables to connect the dock to the iMac. I know it sounds stupid but it works.

Reply to self.

With SMC reboots of both computers there's been no change.

Have been asked to take new MBP into a genius bar. No way. I kept mentioning this forum and that Apple engineers could easily replicate the issue the their labs. Taking a call back tomorrow and will report but likely no change.

With research I find that Thunderbolt 3 can only transform itself into Thunderbolt 2, VGA or HDMI. To get other signals from these MBP ports is to obviously use them as USB-C but USB signals can't support monitors (I don't think).

Question is: whether to sell the iMac and buy a new screen that takes HDMI? Maybe.