How To Downgrade iOS 4.1 To iOS 4.0.x iPhone 4, 3GS, 3G

Posted by dkszone on September 9, 2010

Have you fallen prey to iTunes’ innocent looking update message and unknowingly upgraded to iOS 4.1 ? Don’t worry, as there is a way to downgrade toiOS 4.0.1 (which you can jailbreak using JailbreakMe 2.0), oriOS 4.0.2 (redsn0w 0.9.5b5-5 can jailbreak iPhone 3G, PwnageTool for iPhone 3GS), or the iOS 4 final version. But wait… have you saved your SHSH blobs earlier?

Yes, you can only downgrade iOS 4.1 if you have already saved your SHSH blobs (ECID SHSH) either locally (using TinyUmbrella) or on Cydia’s servers. If you haven’t yet updated your firmware and are just looking for more information, then follow this guide to save your SHSH blobs and also preserve unlock baseband before you upgrade to iOS 4.1. downgrade-ios-4.1

For the rest of you who have already updated your firmware here is how you can downgrade it to iOS 4.0.1 or any other earlier version (iOS 4.0.2, iOS 4, iOS 3.1.3/3.1.2) provided you have SHSH blobs saved for that firmware on your iPhone 4, iPhone 3GS, or 3G.

1. Download iOS 4.0.x firmware IPSW file to your Computer.

2. Edit and save your system’s hosts file, adding the following line:

74.208.10.249 gs.apple.com

Here is how you can

Edit And Save Hosts File In Windows

Edit And Save Hosts File In Mac OSX

What you are in fact doing by changing the hosts file is to trick iTunes into believing that it is communicating with Apple’s servers, while it’s actually talking to Saurik’s server, where your SHSH blobs are saved.

3. Now restore your device to the older firmware you downloaded in step 1. For doing this, open iTunes, and click SHIFT (ALT for OSX) + Restore.

4. Browse and select the IPSW file when prompted by iTunes. Let iTunes restore your iPhone to the selected iOS 4.0.x firmware.

5. After installation, you may come across errors 1015, 1013, or 1011 unable to get out of recovery errors.

6. Here is how you can exit recovery mode using RecBoot. Or you could also use TinyUmbrella’s Kick Device Out Of Recovery’.

That’s it. When your iPhone restarts, you will find it on an older firmware. You can now go ahead and jailbreak it, even unlock it with Ultrasn0w 1.1-1 if you have already preserved baseband 1.59.00.