iphone-4-andiphone-3gsA user named codeblue has discovered this unconfirmed way that allows you to downgrade from iOS 4.0.2 to iOS 4.0.1 without the need of saved SHSH blobs. This can help users to jailbreak their iPhone 4 and iPhone 3GS(new bootrom) who just got a new iPhone that’s already on iOS 4.0.2 or have accidently upgraded to iOS 4.0.2.

This method is not tested by me and many others are saying it didn’t work for them, however you can try and checkout if it works for you. If you make a mess, I am not responsible for any loss. Always backup your data before following such guides, you follow this guide on your own risk.

How to downgrade iOS 4.0.2 to 4.0.1 on iPhone 4/3GS without using Cydia SHSH

  1. Download iOS 4.0.1 for iPhone.
  2. Rename the downloaded file extension(.ipsw) to .zip
  3. Extract the contents of the renamed .zip file.
  4. In the extracted files, look for “buildmanifest.plist” and open it in notepad. Replace all entries "8a306" with "8A400" and save the file.
  5. In the extracted files, look for “restore.plist” and open it in notepad. Replace all entries "8a306" with "8A400" and save the file.
  6. Download iOS 4.0.2 for iPhone
  7. Rename the downloaded file extension(.ipsw) to .zip
  8. Copy all the files from the extracted 4.0.1 firmware and paste them to the extracted 4.0.2 firmware files.
  9. Now, delete all the dmg files that have 002 at the end, leaving only the files that have 001 at the end.
  10. Save the folder as archive(.zip) and rename it back to .ipsw
  11. This step is not necessary but if you do it, it will ensure that you get an SHSH file request for the future by redirecting server to Saurik’s server when iTunes will check if your device is compatible with the firmware version.If you are using Windows:
    - Start notepad in Administrator privileges. To do this, right click on Notepad and click run as administrator.
    -     Open the hosts file from C:/Windows/System32/drivers/etc and add the following line to the bottom of the file and save it.

    12. 74.208.10.249    gs.apple.com

    If you are using Mac
    -     Go to finder and click Go to folder. In go menu enter /etc in input field and clickGo.
    - Look for hosts file, right click it and open with Text Edit.
    - Add the following entry to the bottom of the file.

    74.208.10.249    gs.apple.com

    - Click on Save As and enter the name ‘hosts’ , Where: ‘desktop’, Plain Text Encoding: ‘Westren (Mac OS Roman)’ and uncheck ‘If no extension is provided, use .txt’. Click Save.
    - Drag drop file to /etc folder and follow the instructions.

  12. Your device is now ready for downgrade by restoring. Now connect your device to Computer and turn it off.
  13. Now you have to enter your device in DFU mode. To do this, hold power and home button together for exactly 10 seconds and then release the power button but keep holding home button until USB device is recognized.restore

    If you see the restore logo, that means you have not entered the DFU mode. When you enter DFU mode, the following message appears on iTunes.

  14. Click OK and restore your device to iOS 4.0.1 by holding Shift Key (Windows) or Option Key (Mac), Clicking restore and browsing the .ipsw file created in steps 1 to 10.

To jailbreak iOS 4.0.1, follow these guides

[via ihackintosh, image via gadgetsdna]