Error code
iOS 1604
IOS1604
System Error Code· A POSIX/system errno returned when a system call fails.
What it means
Unknown error during recovery-mode restore — device communication failed partway through..
How to fix it
- Uninstall and reinstall iTunes (Windows) or update macOS.
- Disconnect all other USB devices except the device being restored.
- Restart the Apple Mobile Device service.
- Try from a different user account on the same computer.
Not affiliated with iOS. Answer summarized from the manufacturer's manual linked above; consult that source for the authoritative procedure.
More iOS codes
- 1600Device not in correct recovery or DFU mode for a custom restore.
- 1601USB driver or host-side communication failure during a recovery-mode restore.
- 1602Connection interrupted at the start of a recovery-mode restore — iTunes could not complete the initial handshake.
- 1015Cannot restore to a downgraded firmware version — iTunes detected an attempt to install an older iOS than what Apple currently signs.
- 1110USB configuration or device state error during restore.
- 1394Component or IPSW validation error — iTunes encountered an error validating part of the firmware bundle.
- 14Communication error during restore — the device connection was lost and the IPSW could not be fully written.
- 1671Software update is downloading — this code is shown while the device is in the middle of downloading its update.
- 17Device could not be restored to the selected iOS version — the firmware is no longer being signed by Apple.
- 2001USB communication error during restore — the host-side USB chipset returned an unexpected error.
- 2009Device disconnected during restore — same as 4013 family but reported as a USB timeout by the host.
- 21Device in recovery mode and restore process failed — the restore was interrupted while the device was in recovery mode.