Downgrade iOS 4.2.1 To iOS 4.1, 4.0.2, 4.0.1 On iPhone 4, 3GS, 3G, iPod Touch 4G, 3G


by casey on November 20, 2010

Previously we have posted Jailbreak iOS 4.2.1 GM On iPhone 4, 3G, 3GS, iPod Touch 2G, 3G, 4G With Redsn0w 0.9.6b2. Some curious people have followed the guide and successful to jailbreak iOS 4.2.1 GM on their devices. We already mentioned that Cydia is currently broken on iOS 4.2.x . Cydia for iOS 4.2.x will be ready once iOS 4.2.1 is released for public. But you can use SSH to install apps on your jailbroken device with Redsn0w 0.9.6b2. Si it seems a little pointless to test jailbreak on iOS 4.2.1.

Also it has been noticed that iOS 4.2.1 Golden Master has a new baseband version which makes jailbreakers to come up with downgrade methods from iOS 4.2.1 GM to iOS 4.1, 4.0.2, 4.0.1 or lower. You need to save your SHSH blobs for this method to work.
4.2.1 downgrade


  • Download iOS 4.1 or some other older firmwares for your device as required.


  • Connect your device to your computer, turn off your device and start iTunes.

Step 3:

  • Now you have to put your device in DFU Mode. You can do this by holding Power and Home buttons together for 10 seconds or so.
  • Let go the power button but at the same time hold the Home button.
  • Your computer will now notify you that it as found a new USB device and iTunes will also recognize your attached device.
  • Save this file.

Step 4:

  • Do not follow this step if you are using iPhone 3G or iPod Touch 2G.
  • Now you will add Saurik’s Server address to your system hosts file. The tweak will apparently show iTunes as if it communicating with Apple. In fact it is communicating with Cydia.
  • Find “C:\Windows\System32\drivers\etc\” for Windows and “/etc/” directory for Mac, then locate “hosts” file and Open it in Notepad (for Windows) or TextEdit (for Mac OS X) and add this at the bottom of the file.
  • “”

Step 5:

  • Restore your device to iOS 4.1, 4.02 or 4.0.1 by clicking the iPhone icon on left sidebar of iTunes.
  • hold left “alt” button on Mac (“Shift” button on Windows) on the keyboard and then click on “Restore” then release the alt button, Now Select the iOS 4.1, 4.0.2 or 4.0.1 ipsw file you have already downloaded in Step 1.
  • The rest of work will be done by iTunes automatically.

Step 6:

  • Launch TinyUmbrella to come out of recovery mode.
  • Click on “Exit Recovery” button.
  • You iDevice will now restart.

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