Yes now you can revert back your iPhone 3GS firmware 3.1 to firmware 3.0. Previously we shared method to downgrade your iPhone firmware from 3.1 to 3.0.1, however this time Jay Freeman found a way to downgrade from firmware 3.1 to 3.0. Jay Freeman is the developer behind the well-known Cydia store for iPhone. Note that the process below will only work for those who have saved their SHSH to Cydia Server. You may read more about SSH from this blog post by Saurik. This process will downgrade your iPhone firmware from 3.1 to 3.0 but you baseband firmware will not be downgraded which means you won't be able to unlock it for now.

Update : Unlock iPhone Firmware 3.1 Compatible With PwnageTool 3.1
Update : Unlock iPhone 3G Firmware 3.1 Compatible With Ultrasnow 0.9

1. Download and install iTunes 9 (Find download link at the end of post)
2. Now download firmware 3.0 for iPhone 3GS (Find download link at the end of post)

Note: Don’t use iPhone firmware 3.0.1 because Saurik’s Server does not have signatures for firmware 3.0.1 uptill now.

3. Now you have to block 74.208.105.171 gs.apple.com by using hosts file

For Windows:
Navigate to C:\Windows\System32\drivers\etc\ and double-click on the host file, choose Notepad or Wordpad to open it. In Windows 7 you have to run Notepad as Administrator so right clicking on "Notepad" app, and choose "Run as Administrator".
For Mac OS X:
Mac users can access "/etc/" directory by going through "Go->Go to Folder" from Finder. After finding hosts file, open it via TextEdit.



4. Now add the following code in a new line as shown in the screenshot. Click save and close the hosts file

74.208.105.171 gs.apple.com



5. Connect your iPhone to your computer and put it in DFU mode by: Hold down the power and home buttons for 10 seconds, letting go of the power button but continuing to hold home until iTunes recognizes the device with the message: "iTunes has detected an iPhone in recovery mode. You must restore this iPhone before it can be used with iTunes". At this point your iPhone screen should be entirely black.
6. Now connect your iPhone to your computer and start iTunes 9, in Microsoft Windows click Shift+ Restore and in Mac OS X Option+Restore



7. Now select firmware 3.0 ispw file we downloaded in step 2 and restore it. You might see the following error. Just ignore it

The iPhone "your iPhone" could not be restored. An unknown error occurred. (1015)

8. Just ignore this error and restart the restoring process from Step 6 to Step 7 until you get the 1015 error again. At this point, simply ignore the error and close iTunes as your device has already been successfully downgraded to firmware 3.0

Update : Revert Back from iPhone Firmware 3.1.3 to 3.1.2

Download iTunes 9
Download iPhone OS 3.0 firmware for iPhone 3GS