Update error 4000
Can't get update to work through several attempts. Error 4000
iPhone 8, iOS 14
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Error 4000 is an undocumented error code (at least publicly undocumented). It means that the connection between the phone and iTunes was interrupted in the middle of a sync or update activity. In the past this might have been caused by a flakey USB port, an antivirus or a firewall. However, there is a new cause of this error that is the result of a bug in iTunes for Windows that requires the phone not be locked during the update. I think this has been finally fixed in the latest iTunes update, so try getting that from https://itunes.com/. If not first check your antivirus and firewall (temporarily disable them), but if that doesn’t fix it there are three workarounds for the bug:
- Update over the air, by going to Settings/General/Software Update
- Downgrade iTunes to version 12.8 if you can find a copy - try https://apple.com/itunes
- Temporarily disable the screen lock passcode on the phone before updating using iTunes on Windows
Note that this error should only be a problem for updates; if you are restoring iOS rather than updating it should not occur.