2013 iMac to 2011 iMac TDM not functioning. Command f2 no response at all.

Question

Level 1

13 points

2013 iMac to 2011 iMac TDM not functioning. Command f2 no response at all.

On learning that 2011 27" iMacs won't be supported for Mojave OS I bought a 2013 27" iMac. That way I could use the old 2011 as a second display using a thunderbolt cable and Target Display Mode. The first step is to press Command f2 on the target display (the 2011 iMac). Nothing happens. Same if I try to use the 2013 iMac as the target display. Otherwise, both iMacs work flawlessly. Both iMacs have OS version 10.13.5. One iMac is using a Bluetooth Apple keyboard, the other is using a hardwired large Apple Keyboard. And yes, F2 does work for display brightness when I press fn f2.

Posted on Jun 24, 2018 4:58 PM

Reply

Answer 1

Top-ranking reply

SeaPapp

Level 7

26,492 points

Jun 24, 2018 6:32 PM in response to KenJr

Are you using the correct cable?

If Command-F2 doesn't work

If your iMac doesn't switch to Target Display Mode when you press Command-F2, check these things:

Make sure that the iMac you're trying to use as a display supports Target Display Mode.
Target Display Mode works only when your primary Mac is logged in to a macOS user account. For example, if your first Mac is at the FileVault login screen, pressing Command-F2 on your iMac does not enable Target Display Mode. You must first log in to your Mac (using a regular display, if necessary) before you can use an iMac in Target Display Mode.
Make sure that you're pressing Command-F2 on the keyboard that's connected to the iMac you want to use as a display.
In Keyboard System Preferences, if the checkbox is enabled for "Use all F1, F2, etc. keys as standard function keys," the key combination changes to Command-Fn-F2.
Make sure that your Mini DisplayPort or Thunderbolt cable is connected to both computers.
If you're currently logged in on the iMac you want to use as a display, try logging out to return to the login window. Then press Command-F2 again.
Some older Apple keyboards and third-party keyboards might not allow Command-F2 to toggle display modes. If this happens, use the keyboard that came with your iMac to toggle Target Display Mode on and off.
If your iMac is currently started up in Windows, it won't enter Target Display Mode. Target Display Mode isn't supported in Boot Camp.

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

Reply

Answer 2

Jun 25, 2018 12:02 AM in response to KenJr

KenJr wrote:

Each of the iMacs have lightning bolt icons above the Thunderbolt ports.

It could be a bad Thunderbolt cable. Can you try the cable with another Thunderbolt peripheral, or try another cable?

Reply

Answer 3

Jun 25, 2018 7:28 PM in response to KenJr

KenJr wrote:

I am wondering though if maybe TDM doesn't work with High Sierra version 10.13.5 (keeping in mind that most of the thinking that goes into doing these updates is centered around Retina display devices .. TDM doesn't work with retina screen iMacs). Maybe TDM inadvertently left out of 10.13.5 update.

TDM is hardware (and firmware), and shouldn't care what OS is installed. It should work even with a blank disk. With TDM on the 2011 iMac, it acts as a display. The 2013 iMac should just see it as another display.

You may be able to check the Thunderbolt cable using System Information (Option-click the  at top-left of screen).

Select Thunderbolt under Hardware in the left column and see what is listed. Do this on both iMacs, then connect them with the Thunderbolt cable, refresh both screens (⌘R), and see if each now shows the other iMac as connected.

Make sure the Thunderbolt plugs are pushed in all the way (no metal showing).

Reply

Answer 4

SeaPapp

Level 7

26,492 points

Jun 25, 2018 3:14 AM in response to KenJr

Try resetting the SMC on both iMacs How to reset the System Management Controller (SMC) on your Mac - Apple Support

Reply

Answer 5

Jun 24, 2018 11:24 PM in response to KenJr

Are you sure it's a Thunderbolt cable, not a Mini DisplayPort Cable? The plugs are the same, but a Thunderbolt cable should have a lightning bolt icon on each plug.

Reply

Answer 6

Jun 24, 2018 11:35 PM in response to KenJr

Does the 2011 iMac have lightning bolt icons next to the Thunderbolt ports?

Reply

Answer 7

KenJr Author

Level 1

13 points

Jun 25, 2018 9:19 PM in response to Malcolm J. Rayfield

Looking at the Thunderbolt hardware - Thunderbolt bus information, both displays show a port status of "No device connected". Same after refreshing both screens (command R).

By the way, I did take the cable to the Apple store where they took it in back and put it on some kind of testing apparatus; the cable checked okay.

Also, I've been in contact with Apple Support. We've gone through several procedures, so far to no avail. Files are currently being downloaded for their engineering team.

P.S. Thanks for the hardware/firmware comment (system doesn't care what OS version is installed). That thought (maybe an update problem) was really gnawing at me.

Reply

Answer 8

KenJr Author

Level 1

13 points

Jun 25, 2018 12:14 AM in response to Malcolm J. Rayfield

I'm beginning to believe that the problem is with the cable. I do wish I had another cable around to test out your idea Malcolm.

Reply

Answer 9

rkaufmann87

Level 10

148,624 points

Jun 24, 2018 6:26 PM in response to KenJr

Are you using Mojave, if so you should not be posting on this forum as it's beta software at this point and beta software is not to be discussed on these forums per the Terms of Use we all agreed to. If you are using it please post on the appropriate forum!

Reply

Answer 10

KenJr Author

Level 1

13 points

Jun 24, 2018 11:16 PM in response to SeaPapp

I'm using 1M Startech Thunderbolt cable - the type of Thunderbolt cable that properly fits into 2011/2013 iMac Thunderbolt sockets. Furthermore, I've followed, in detail, each of the eight recommendations noted in the Apple "If Command-F2 doesn't work" Notes.

Reply

Answer 11

KenJr Author

Level 1

13 points

Jun 24, 2018 11:23 PM in response to rkaufmann87

I'm currently using High Sierra 10.13.5. I bought the late 2013 iMac because it's on the list of devices that will be able to support the soon to be released Mojave OS. My 2011 iMac is on the list of devices that won't be able to support Mojave.

Reply

Answer 12

KenJr Author

Level 1

13 points

Jun 24, 2018 11:31 PM in response to Malcolm J. Rayfield

Unfortunately the cable does have the Thunderbolt lightning bolt icon on each plug. I'd like to have discovered otherwise so I could end this frustrating debacle.

Reply