Target Display Mode using 2019 MBP and 2012 iMAC

Question

I currently have:

2019 MBP on MacOS 10.14.6
2012 iMAC on MacOS 10.14.6 (thunderbolt 2)

I am connecting them to each other using a Thunderbolt 2 to Thunderbolt 3 adapter, both of which are brand new.

I was able to trigger target display mode ONCE. Then cmd + F2 stopped responding entirely. Things I've tried:

reset the PRAM/NVRAM on both devices
cmd + F2 + fn
every combination of the ports on each end
booted the iMAC in safe mode (can't do it on the MBP; it's a work laptop)
tried initiating TDM by connecting iMAC to MBP 2014, still no dice on cmd + F2

I've perused all the Apple support pages and similar stackexchange questions to no avail and now I'm at my wit's end. Did anybody face something similar and was able to resolve?

do you have a Retina display. According to one source Target display mode not available on iMacs with retina displays. — Natsfan, Jun 10 '20 at 21:34

score 0 · Answer 1 · answered Mar 19 '21 at 14:20

0

Did you use a 'Thunderbolt' or 'Thunderbolt 2' cable to connect the two macs? Also judging by your description the iMac has Mojave installed whereas TDM would work only on an iMac with High Sierra or below. For reference please follow this official Apple article: https://support.apple.com/en-us/HT204592

answered Mar 19 '21 at 14:20

rraimis11

1

?? The Apple tech who talked about TDM on my 2019 MBP with Big Sur is ignorant? – WGroleau Mar 19 '21 at 16:47

score 0 · Answer 2 · answered Dec 14 '21 at 18:09

I recall that you have to be logged out on the target iMac for target display mode to work. I recall seeing this in a YouTube video but not where, and it is pretty obscure so I doubt I'll find it again. otherwise I'd link to it. Apparently once logged in something interferes with the Command+F2 keyboard macro.

Also, keep in mind this is a feature Apple no longer officially supports. They stopped supporting this feature some time ago and so any software that was required to make this work may no longer be in place. The tech support people at Apple will no doubt be helpful geeky types and if you contact them then they will do their best to make this work for you but that's not going to restore whatever old software was in place that made this work a decade or so ago.

I think this video titled "How to connect your old 2009 imac to new 13" M1 Macbook Pro as an External Monitor" describes the method you mention. However, it works only if the iMac has a mini DisplayPort. Unfortunately, only certain iMacs from 2009 and 2010 have a mini DisplayPort according to the Apple Support page titled "Identify the ports on your Mac". So the method is unlikely to help in this case. — Alper, Dec 14 '21 at 18:42

score 0 · Answer 3 · answered Sep 26 '22 at 12:10

I have been using a 2013 iMac in Target Display mode with a 2018 MacBook Pro for 2-3 years, with a new Thunderbolt 2 to Thunderbolt 3 adapter as you describe (both from Apple).

However I recently changed jobs and got a 2019 MBP and can no longer use Target Display mode.

I can't find a definitive answer to this anywhere else, but it seems either an update to the OS on the newer MBP or something about the new hardware means it doesn't work with the new MBP, while it does still work with an older MBP.

Target Display Mode using 2019 MBP and 2012 iMAC

3 Answers3