Downgrade from iOS 4.0.2 to iOS 4.0.1 in case you have not Saved SHSH Blobs [Read Update]

If you have already saved your SHSH Blobs on Cydia server or locally, you can head over to our previous post to downgrade from iOS 4.0.2 to iOS 4.0.1. But in case you don’t have SHSH blobs saved, follow this step by step guide to restore iPhone 4/3GS/3G etc to iOS 4.0.1.

downgrade ios 4.0.2

Step 1: Download both iOS 4.0.2 and iOs 4.0.1 on your PC. (download links at the bottom of this post)

Step 2: Extract only iOS 4.0.1 with WinZip or WinRar in separate folder. You will have to change the extension of iOS from .ipsw to .zip to extract them.

Step 3: From the iOS 4.0.1 extracted files open buildmanifest.plist file with notepad and replace all the – 8A306 with 8A400. Save the file. Now open the other file restore.plist and again replace all 8A306 with 8A400. Save this file too.

Step 4: Rename iOS 4.0.2 file extenstion from .ipsw to .zip and open it with WinZip or WinRar. Do not extract this to any folder. Now copy all the files from iOS 4.0.1 folder and paste in iOS 4.0.2 opened archive. Overwrite the files if/when asked.

Step 5: In iOS 4.0.2 delete all dmg files which have 002 at the end and leave only those files which have 001 in the file.

Step 6: Zip the iOS 4.0.2 folder again and change the extension from .zip to .ipsw

Step 7: Optional: (this helps ensure you get an SHSH file request for the future, but should not be necessary to just restore 4.0.1).  Add the 74.208.10.249 gs.apple.com line to the host file. Follow the steps below how to change this.

Windows

  • Open Notepad with administrator privileges and then right-click on the icon of notepad and click on “Open as administrator”
  • Now that Notepad is open Go to folder C:/WINDOWS/system32/drivers/etc and open the file
  • Add the following line at the end of the document and save it: 74.208.10.249 gs.apple.com

Mac

  • Navigate to Go -> Go to Folder and enter the path /etc
  • Open the file hosts with TextEdit, add the following string 74.208.10.249 gs.apple.comand save the file to your desktop.
  • Now return to the previous folder by following the same method and copy the text within this file by replacing the original file (If prompted for a password enter it and click OK)

Step 8: Put your iPhone in DFU mode, open the iTunes and restore your phone to iOS 4.0.1. To learn how to put your iPhone into DFU mode and restore, follow the steps 4, 5, 6, and 7 in this post.

Now you can use jailbreakme to jailbreak your iPhone and ultrasnow to unlock and make it free from any carrier.

Note: this only works due to the similarities in 4.0.2 to 4.0.1 and 4.0. This will not be a way to downgrade to 3.1.x and may not work in future firmware updates.

[via gadgetsdna]

Downloads:

Update 1: Many iPhone 4 users have reported that this method didn’t work for them, but some iPhone 3GS users sent positive feedback. In case you have iPhone 4, try using the older version of itunes and even then it doesn’t work, don’t waste your time by making more attempts. Here is guide for those who want to downgrade but have saved the SHSH blobs.

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