The iPhone "xyz" could not be updated. An unknown error occurred (4000)
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).
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?
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 :
- connect via USB
- temporarily disable the passcode (see below)
- update iOS via iTunes
- re-enable the passcode
To temporarily disable the passcode :
go to Settings -> Face ID & Passcode -> Turn Passcode Off
>> Face ID & Passcode
>> Turn Passcode Off
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.