2018 MacBook Pro Target Display Mode Not Working

Same here. 13-in 2018 MBP to Late-2013 iMac 27", via TB2 and USB-C adapter, all-Apple from one end to another, running 10.14.5 everywhere. Sometimes, my iMac will blackscreen me if I'm logged in, and sound won't go through the iMac speakers (the option is selected but noting will come out.

Mind you, the iMac went through its share. Right now, even with my RAM upgrade, it can't seem to sync my iCloud drive and Time Machine at the same time. Also, I'm not sure if I have the original keyboard (moved twice since I got it), but I tried with a wired extended keyboard too, to no avail. Could it be that the iMac will blackscreen me if it's too busy?

ThunderBolt-3 to -2 cable.

A dock may re-drive the signals, you need a direct connection.

If you only want to hold the CMD-F2 keys, you can go to system prefs > keyboard > select "use F1, F2, etc. as standard function keys"

Did not solve the problem for me. 2018 MBP with mid 2011 27" iMac, using thunderbolt on iMac to thunderbolt on USB-C docking station on MBP. Just upgraded to mojave 10.14.2. My iMac does nothing. Doesn't seem to recognize key strokes at all. Tried all the suggestions. Original bluetooth keyboard no longer works. Have McCally wired replacement with identical mac keyboard. Tried original anyway. Nothing. Aargh!

• USB Type-C™ is a specific feature of a product, it is not a generic description. Think of “USB Type-C” as an adjective not as a noun. 

-- according to:

http://www.usb.org/developers/usbtypec/USB_Type-C_Language_Product_and_Packaging_Guidelines_FINAL.pdf

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This adapter is available for sale by Apple:

Thunderbolt 3 (USB-C) to Thunderbolt 2 Adapter - Apple

You would need a ThunderBolt-2 cable as well.

The cables required for different setups are described in this article as well:

Use your iMac as a display with Target Display Mode - Apple Support

.

katbay-

Are you using models supported as mentioned in that article?

Exactly which models are you using?

Are you booting up the iMac in the usual way, then once running normally, using the Command-F2 directive to initiate target Display Mode?

iMac mid-2011 27" running 10.13.6 to MacBookPro 15 2018 running Mojave 10.14.2

Booting iMac as usual, then Command-F2.

Only thing I can think is to replace Thunderbolt 2 cable. Currently using Cable Matters [Certified] Thunderbolt Cable/Thunderbolt 2 Cable Black 6.6 Feet

Suggestions?

It was my third party keyboard that didn't accept Command F2. I tried this yesterday before adding the adaptor, but with the adaptor, it works. There should be a popup window or something when another monitor is connected, or a detector of some kind. My old bluetooth keyboard barely works so I replaced it. Thank God I didn't get rid of it and it worked for this. Thanks for all your help.

Interesting. I've just been using my plug-in Mac keyboard that came with my iMac. No third party anything (except my mouse). Also as noted in an above reply I got it to work today for some reason I can't determine. I also noted I need to use CMD+Fn+F2 and hold it down for about a second to work (despite my F keys being mapped as normal, whatever!).

Very interesting. As mentioned in my previous posting, I was having the black screen issue when connecting a 2018 MBP to a late-2012 iMac, both running the latest Mojave version 14.3 I have no dock, and would be really annoyed if I had to spend several more hundred dollars on random hardware to make this work. Luckily, while on the phone with support the TDM started working without the support person actually doing anything, so I dodged that bullet for now!

I know about the keyboard thing katbay. I bought another keyboard for the new Mac and kept the old one for the old iMac.

I know this is not a Mac Mini thread but it is the closest thing I can find re the 2011 iMac. I am rapidly coming to the conclusion that Apple has just not tested this new Mac mini properly. I don't think that the number of permutations and combinations is an excuse - Apple has the scale and resources to put a team of 100 persons on it to test. The recommendation people on here make is Mojave. I cannot upgrade a 2011 27i iMac to Mojave. Apple says that a 27i iMac should work in TDM with a Mac mini with Thunderbolt. I think this is probably just wrong. This kind of incorrect information from Apple, on a new product and how it works with another Apple product, is rather disgraceful for a company the size of Apple.

It's a learning point. And although I would not have bought the new Mini had I known all this, for the first time in years I now have a non Apple component - a new display which cost a lot less than the recommended screens in the Apple Store and is still 4K. It could be a blessing in disguise. After all, the more you learn about technical specs etc., the more you learn how expensive Apple products are for what you get. Not so much of a problem when they work...

I agree with dom63. Mojave is not necessary on the iMac for TDM. I am running High Sierra on my 2011 iMac. Once you get the right cables, TB adaptor and keyboard, it should work. Hope you figure it out. Rootin' for ya.

Hate to disagree but I have a late 2013 27" iMac running ver 10.14.3 and a new MacBook Pro 15" on the same version and I can't get the MacBook Pro to recognize the iMac. I have to say this myth is busted for now. All cables and adaptors are Apple products (no 3rd party cables).

The connection described in the question is valid:
Use your iMac as a display with Target Display Mode - Apple Support

I have the same problem. I use my 2011 iMac (running on High Sierra OS) for target display to MacBook Pro (Retina, 15-inch, Mid 2014). The iMac was running very smooth as my target display. A few days ago, I just got 2018 MacBook Pro (running on High Sierra OS version 10.13.6 (17G2307)) and it's no longer able to connect to the 2011 iMac. After I read the discussion here, I chat with the Apple support. He told me to use Thunderbolt 3 (USB-C) to Thunderbolt 2 Adapter. I will get this cable tomorrow and will give you an update.