Target Display Mode not working with USB-C MacBook Pros

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Level 1

9 points

Target Display Mode not working with USB-C MacBook Pros

I purchased Apple's Thunderbolt 3 > Thunderbolt 2 adapter specifically to be able to continue using Target Display Mode on my 2010 iMac 27" with USB-C MacBook pros, but I have not been able to make it work. Target Display Mode continues to work with a variety of older MacBook Airs that have Thunderbolt 2 ports, but I have not been able to make it work with any of the USB-C MacBook Pros that I have tried it with.

For the record:

I have tried CMD-fn-F2 on the MBPs
I have tried using each of the USB-C ports on the MBPs
I have tried with the iMac logged in and without
I have tried CMD-F2 on the iMac
I have restarted both machines
I have reset the PRAM on both machines
I have checked in the display settings on the MBP
The iMac is running 10.13.6 (latest version for that machine)

My current MBP is a 2019 13" with touchbar and 4 USB-C ports running 10.15.7. My older MBP was the older, slower model with 2 ports. When I purchased my first MBP with USB-C I asked at the Apple Store why it didn't work, and they claimed that it was not possible with that machine, but I have since seen it done on YouTube by many people.

Target Display Mode remains plug-and-play on all of the older machines, with no F2 or other key combination necessary. I only need to choose whether I want to mirror displays or expand the desktop.

With all of that in mind, the most likely culprit seems to be the adapter, but I want to see if there is something I may be missing before making an appointment and taking half a day to haul both machines in to the shop.

MacBook Pro with Touch Bar

Posted on Sep 28, 2020 9:32 AM

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Answer 1

Kappy

Level 10

362,017 points

Sep 28, 2020 11:15 AM in response to Dane Thomas

Target Display Mode no longer works with Macs from 2019 and later. Please see Use your iMac as a display with Target Display Mode - Apple Support. However, they will work with an external display: Use Mac notebook computer in closed-display mode with an external display.

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Answer 2

Sep 29, 2020 12:55 PM in response to Dane Thomas

You do not use a Thunderbolt 2->Thunderbolt 3 adapter to connect

the MacBook Pro Thunderbolt 3 to any MiniDisplay Port or DisplayPort

monitor. You need a USB-C to DisplayPort or a USB-C to MiniDisplay Port

adapter. These are not the same thing as a Thunderbolt 2->Thunderbolt 3 adapter.

https://www.apple.com/shop/product/HN8B2ZM/A/mophie-usb-c-cable-with-mini-displayport-connector?fnode=3d4391186ce0eb7823ec2a3713b4e7e5a8678806e3fe42a3f80b687762bb301c3a3c51dcb3ca6b31d8bebc812f89e1ae029753bdfeca48182079cf819c2c36b9cf5e458d33b1c50c1b57456fff636f70949e7633e85a70064c332d7c37ffdf77

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Answer 3

Dane Thomas Author

Level 1

9 points

Sep 28, 2020 12:27 PM in response to Kappy

From your link: "You can connect any of these older iMac models to another Mac from 2019 or earlier for use as an external display."

My current MBP is from 2019, so according to Apple it should work. My previous MBP was from 2016. Neither of them can engage Target Display Mode despite my having followed all of the instructions on that page.

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Answer 4

Dane Thomas Author

Level 1

9 points

Sep 28, 2020 12:33 PM in response to Dane Thomas

One more thing - I have extensive experience using each of the MBPs (2016 and 2019) as well as the older MacBook Airs with a wide variety of external displays, both in mirrored and screen extension modes. No problems with any of them.

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Answer 5

Dane Thomas Author

Level 1

9 points

Sep 29, 2020 12:24 PM in response to BDAqua

Good question. I will need to re-watch the videos to see which models of iMac 27" were used.

All I know is that it is frustrating to be able to use Target Display Mode on my iMac with MacBook Airs from 2011, 2013, and 2014 but not with MacBook Pros from 2016 and 2019, despite my having invested in the adapter that should make it possible.

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Answer 6

Dane Thomas Author

Level 1

9 points

Sep 29, 2020 11:15 AM in response to BDAqua

If it works for others who have MBPs with usb-c ports (as seen on the YouTube videos), there should be some way to make it work for me.

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Answer 7

BDAqua

Level 10

250,259 points

Sep 29, 2020 5:26 PM in response to woodmeister50

👍

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Answer 8

BDAqua

Level 10

250,259 points

Sep 28, 2020 2:20 PM in response to Dane Thomas

The 2010s don't use Thunderbolt, but MDP...

27-inch iMac models introduced in 2009 and 2010: Use a Mini DisplayPort cable to connect your iMac to a Mini DisplayPort or Thunderbolt or Thunderbolt 2 port on the other Mac.

Target display mode requires macOS High Sierra or earlier on the iMac used as the external display.

https://www.amazon.com/DisplayPort-Adapter-QCEs-Thunderbolt-ChromeBook/dp/B073CVK6P6/ref=asc_df_B073CVK6P6/?

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Answer 9

Dane Thomas Author

Level 1

9 points

Sep 29, 2020 1:15 AM in response to BDAqua

You are of course, correct regarding the type of cable that is necessary.

You seem however to have missed the part where I verified that using my iMac in Target Display Mode currently works successfully with several older MacBook Airs.

I have the correct Mini DisplayPort cable to connect the Mini DisplayPort outlet on my iMac with the Thunderbolt 2 ports on the MacBook Air computers. It works as it should.
My iMac is running macOS High Sierra 10.13.6, as noted in my original post.

Once again, I am trying to use the Apple Thunderbolt 3 > Thunderbolt 2 adapter to connect MacBook Pros (2016 and 2019) with the exact same Belkin Mini DisplayPort cable that works with the MacBook Airs, but it does not work with the MacBook Pros.

This video makes me think that it should not be impossible: https://www.youtube.com/watch?v=v4r363c95tk

Here are several more videos showing essentially the same thing: https://www.youtube.com/results?search_query=target+display+mode+imac+macbook+pro

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Answer 10

Dane Thomas Author

Level 1

9 points

Sep 30, 2020 12:52 AM in response to woodmeister50

Thank you very much for your suggestion.

According to this link https://support.apple.com/en-us/HT201736 , "Thunderbolt and Thunderbolt 2 are not the same as Mini DisplayPort. They have the same shape, but use different symbols on the cable and port. However, this port does support Mini DisplayPort for video output, so you can use a Mini DisplayPort cable to connect a Mini DisplayPort display."

The ports on my MacBook Airs that can successfully engage Target Display Mode are Thunderbolt 2.
The port on my 2010 iMac 27" is Mini DisplayPort.
The adapter that I am using with my MacBook Pros is the same one that works successfully in the YouTube videos: https://www.apple.com/shop/product/MMEL2AM/A/thunderbolt-3-usb-c-to-thunderbolt-2-adapter?fnode=7f698f4188ff8d8c44a39294e6d4409687559929278e4faeb41d496cc56d02793559f1cfefa922ba279962fc14a758a0186c180bfac8ecef5a90c3894a6ca5015c81b0835f0b4fcc170bd09b31083044303cd89f9a9de91fe7959a2eec002279c7fe1fda43bb132818e692c514802f00&fs=f%3Dadapter%26fh%3D459d%252B45b0

What I had not considered prior to your post is that the problem might be the Belkin Mini DisplayPort cable that I am using. It successfully connects the MacBook Airs to the iMac so I thought it should also work with the MacBook Pros, but I have not yet tried a Thunderbolt 2 cable instead.

The Mophie USB-C>Mini DisplayPort adapter cable that you linked to may also work, though it does not list my 2010 iMac 27" as being compatible nor does it claim to support Target Display Mode functionality.

Thanks again for your post. It is a bit of a relief to realize that I had not considered those two potential solutions. I will try one or both of them and report back with the results.

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Answer 11

Sep 30, 2020 7:37 AM in response to Dane Thomas

"The ports on my MacBook Airs that can successfully engage Target Display Mode are Thunderbolt 2.

The port on my 2010 iMac 27" is Mini DisplayPort."

That works with a Mini DisplayPort cable because the Thunderbolt 2 ports on a computer can also act as Mini DisplayPort. This is not the case with the Thunderbolt 2 port on Apple's Thunderbolt 3 adapter.

About the Apple Thunderbolt 3 (USB-C) to Thunderbolt 2 Adapter - Apple Support

"This adapter is not compatible with displays that use DisplayPort or Mini DisplayPort, ... Thunderbolt and Thunderbolt 2 are not the same as Mini DisplayPort , though the ports have the same shape."

Using a Thunderbolt cable won't help because the port on the 2010 iMac is Mini DisplayPort only, and won't work with a Thunderbolt cabvle, even if the Thunderbolt plug fits.

You need a USB-C to Mini DisplayPort cable. There are others besides Apple's, such as:

https://www.startech.com/en-us/audio-video-products/cdp2mdpmm6b

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Answer 12

Dane Thomas Author

Level 1

9 points

Sep 30, 2020 9:13 AM in response to Malcolm J. Rayfield

Thanks!

I suspect that a good deal of my confusion has been caused by my seeing that adapter work on the videos, but not realizing that the iMacs being used were new enough to have a Thunderbolt 2 port rather than a Mini DisplayPort like mine.

I have ordered a USB-C to Mini DisplayPort adapter which should work with the Mini DisplayPort cable that has proven to work with my MacBook Airs. Fingers crossed...

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