Update : iREB Version 4.1 released ! Link at the end of the post.

New version of iREB for all iOS 4.1 devices is now available for download. You can use it to bypass 1604, 1603, 1602, 1601, 1600 error in iTunes during custom iOS 4.1 firmware restore which has been created using either Sn0wbreeze or PwnageTool.


This is what error reads:

The iPhone “-” could not be restored. An unknown error occurred (16xx).

iREB V4.0.x/4.1 Release 2 supports the following devices :

• iPhone 2G
• iPhone 3G
• iPhone 3G[S] (old & new bootrom)
• iPhone 4
• iPod Touch 1G
• iPod Touch 2G (MB & MC)
• iPod Touch 3G
• iPod Touch 4
• iPad
• Apple TV 2 

Step 1: Start iTunes 10.x and put your iOS device into DFU mode:
Press and hold the Home button and the Power button at the same time. After exactly 10 seconds release the Power button. Continue holding the home button until you iTunes pops up a message telling you that it has detected an iPhone in recovery mode. At this point your iPhone/iPod touch screen will remain black.


Step 2: Now close iTunes and Start iREB on Windows.


Step 3: Simply select your device and wait for a few seconds until you get white or a red screen on your iPhone or iPod touch.

Step 4: Now start iTunes again and select your iOS device from the sidebar in iTunes. Now press and hold left “alt” button (“Shift” button on Windows) on the keyboard and then click on “Restore” (Not “Update”) button in the iTunes and then release the “Shift” button. Select the required custom .ipsw file and restore it.
That’s it! iTunes should now be able to restore your iPhone or iPod touch to the latest iOS 4.1 firmware without any problems. Hopefully you wont get any errors this time around!


Download iTunes 10.1 for Windows and Mac
Download iREB for Windows


Please note that iREB is NOT a jailbreaking utility but it aids in jailbreaking iPhone or iPod Touch.