This post will explain how to fix iTunes errors 20 & 1600 during downgrading iOS. This problem is pretty common these days as many iDevice users were trying to downgrade from iOS 5.1.1 to lower versions to be able to jailbreak their devices. By the way today Apple closed signing for iOS 5.1 which means that downgrade to this version became much more complicated. If you are performing the device downgrade the we assume that you know what you are doing. Perform all the actions at your own risk. Note: This method involves redsn0w 0.9.9b1 or higher which can be downloaded using this links: Mac, Windows and corresponding firmware for your device (download link)

How to fix iTunes errors 20 & 1600 while downgrading with redsn0w:

Before taking any further actions don't forget to save your SHSH blobs with TinyUmbrella or iSHSHit. You can also do that with redsn0w within Extras menu but i personally prefer to backup first. Step One: Launch redsn0w and go to Extras. Step Two: Redsn0w might require your device's IPSW for this process so use link above to download it. Step Three: After that choose Select IPSW from the Extras menu and specify the path to downloaded IPSW. Step Four: After the program successfully identifies your firmware click OK and then NO unless you are on the new bootrom of iPhone 3G or iPod Touch 2G. Step Five: Press Pwned DFU within Extras. Step Six: In order to go into DFU mode follow redsn0w's instruction on read the guide to proceed successfully. Step Seven: Now your device will be put into pwned DFU state which fixes errors 20 and 1600. Step Eight: Now go to iTunes, hit Shift+Restore (Alt/Option+Restore if you're on Mac) and select your firmware file. Step Nine: Wait until iTunes finishes restoring your firmware. Step Ten: New firmware is now installed on your iDevice. Here is the video tutorial to make your life even easier: Now you need to activate your iPhone/iPad/iPod Touch. If you have original SIM there will be no problem with activation. But if you don't have such card you have several options. Use redsn0w (manual here) or sn0wbreeze (manual) to activate your iPhone. Please feel free to comment below and let us know if you managed to fix those errors on your device. Don't forget to share, like and subscribe as well.