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Using iTunes to update my iPhone, I got:

Das iPhone "xyz" konnte nicht aktualisiert werden. Ein unbekannter Fehler ist aufgetreten (4000)

English:

The iPhone “xyz” could not be updated. An unknown error occurred (4000).

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I could not solve it with the Apple recommended answer at I got Error 4000 when updating iPhone asking you to:

  • update iTunes
  • update the pc
  • plug in the cable directly (I have not done anything else anyway)
  • Restart both pc and iPhone
  • Switch off antivirus and firewall in all possible options

How to fix this? And if there is no fix, which workaround can help?

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  • Have you had a look at the apple forum: discussions.apple.com/thread/250591032
    – X_841
    Jan 18, 2021 at 20:33
  • Yes, I invested hours to find out that it was that simple, and the apple forum (exactly that link as well) did not help. Good that you remind me of switching on the antivir and the defender again ;). Though I see now at the very bottom "Finally just put iPhone into Recovery Mode and did an update. SUCCESS. It did the 12.4.1 update and all seems fine." Probably that would have helped as well. But the easiest solution is the answer below. Jan 18, 2021 at 20:41
  • I just now realized that you answered your question yourself. Sorry I was confused, but there is nothing to solve anymore I realize. To be honest though, I think most people will try your answer anyway because it is the more intuitive way, however, for those not realizing it this may be helpful.
    – X_841
    Jan 18, 2021 at 20:51
  • @X_841 no problem. Yes and no. I think that iPhone data management with iTunes is so extremely UN-intuitive that such easy answers do not really reach your mind anymore when you are stuck in other issues. No one has any intuitive approach anymore after dealing for hours with a sync problem due to an outdated *.itl library with no option to delete voice memos in iCloud. Then you lose the last intuition. ;) Jan 18, 2021 at 20:59

2 Answers 2

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This is a bug in iTunes when updating iOS via iTunes over USB, where the update will fail if there is a passcode set on the iPhone, and even if the iPhone is in unlocked state when initiating the update.

It exists in version 12.11.3.17 which I am currently on, and also on some of the previous versions (I have no idea in which version this bug originally appeared). I am on Windows 10, 1909 build 18363.904.

The solution is :

  1. connect via USB
  2. temporarily disable the passcode (see below)
  3. update iOS via iTunes
  4. re-enable the passcode

To temporarily disable the passcode :

go to Settings -> Face ID & Passcode -> Turn Passcode Off

>> Face ID & Passcode

Face ID & Passcode

>> Turn Passcode Off

Turn Passcode Off

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I could not get it to work in iTunes, thus here is just the workaround on the iPhone instead, and not the fix for the iTunes problem.


Just update your iPhone using your iPhone update function, not the one offered in iTunes.

I have overseen another possible solution in the link of the question:

"Finally just put iPhone into Recovery Mode and did an update. SUCCESS. It did the 12.4.1 update and all seems fine."

Probably that would have helped as well. But the easiest solution is just to update your iPhone as you would do anyway if you did not have iTunes.

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  • 1
    Your suggestion of updating via Wifi is not a fix, merely a workaround. Some environments only have intranet access via wifi and internet only on computers, some environment don't even have wifi at all.
    – mach128x
    Aug 4, 2021 at 16:45
  • @mach128x I would be happy to make the update work in iTunes as well. I do not know how to do this. And then this workaround (you are right, answer is now edited) is still the way to go, it took me far too long to find this workaround, therefore the sharing. If the Wi-Fi around you is just intranet, you can access a full Wi-Fi network somewhere else. Aug 5, 2021 at 8:15

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