Hello Jaxov, need help here. Few days back, I am trying to jailbreak my iPhone 4 on iOS 4.2.1 using Sn0wbreeze 2.5.1, but during the custom firmware restoration process, iTunes throws Error 21. This is a used iPhone 4 and it was jailbroken on iOS 4.3.1 using PwnageTool but the previous user said he did not encounter this error. What do I need to do to fix this error? My iPhone is dead. Please help, I’m a novice. Thanks in advance.
Asked by: Patrick from Jersey City, New Jersey
Anyway, to fix iTunes’ Error 21, you must put your iPhone (iPad or iPod Touch) into DFU mode. If you don’t know how to put your iOS device into DFU mode, then you can follow the step by step guide posted below:
Step 1: Connect your iPhone (iPad or iPod Touch) to your Mac or PC via USB cable (USB cable) and then launch iTunes.
Step 2: Then hold down the Home and Power button at the same time for 10 seconds.
Step 3: Release the Power button after 10 seconds but continue holding the Home button and wait for iTunes to detect your iPhone in recovery mode.
Step 4: Once your iPhone (iPad or iPod Touch) is in DFU mode, you should see nothing on its screen. It should be completely blank.
That’s it! You can now restore custom IPSW on your iPhone and hopefully this time you will not get iTunes Error 21.