How-to Fix An unknown error (1603)

How-to Fix An Unknown Error (1603) while updating iPhone firmware.

The iPhone “iPhone” could not be restored. An unknown error occurred (1603).

Fix 1603 Unknown Error by following these steps:

1. Download iReb latest version
   
   iReb can fix 1600, 1601, 1602, 1603, 1604 error on iTunes.

2. Run iReb
3. iReb will kill (close) iTunes software and guide you how-to enter DFU mode.
4. Follow the guide to enter DFU mode.
   If your device was already in DFU mode, you don’t need to do anything, because iReb will be searching for DFU of any connected device.

   

   When the device found in DFU mode, iReb will automatically start exploiting the iPhone and let you to restore custom firmware.

   

5. Once done, Your device is now in a PWNED DFU mode state (black screen).
6. Do not click OK until you have finished restore the custom firmware.

   

7. You may now launch iTunes and do SHIFT + Restore, to restore the custom firmware.
8. Done. The custom firmware has been installed on your device. You may either setup as new phone or restore from previous backup. You can close iReb when the firmware has been installed.