3G[S] 3.1 Now Downgradable!!!

Saurik, the developer behind Cydia has found a way to downgrade iPhone 3G[S] from 3.1 to 3.0. This process will only work for those who have saved their SHSH to Cydia Server, for more on SHSH, read the complete detail blog post by Saurik here. Also to note here is that while this method will help you downgrade your firmware from 3.1 to 3.0, your baseband will not be downgraded which means you cant unlock it for now.

The Following Guide will help 3G[S] users downgrade from the newly released 3.1 firmware to 3.0.

Step 1: Download iPhone firmware 3.0 for iPhone 3GS.

Step 2:Download and install iTunes 9.

Step 3: Navigate to C:\Windows\System32\drivers\etc\ and locate “hosts” file or Mac users can get to “/etc/” directory by going through “Go->Go to Folder” from Finder.

Step 4:Open this “hosts” file in Notepad (for Windows) or TextEdit (for Mac OS X) and add this

74.208.105.171 gs.apple.com

(I found that i had to copy the “host” file to my desktop and then make the changes and copy it back to the “etc” folder)

Step 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.

Step 6:Start iTunes, press and hold shift key and then click on “Restore”.

Select the firmware 3.0 .ipsw file you downloaded in Step 1and restore it. During the restore process, iTunes will throw you 1015 error which will say:

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

Just ignore this error and restart the restoring process from Step 5 to Step 6 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.

Step 7: You can now jailbreak your iPhone which you have downgraded from firmware 3.1 to 3.0.

Please note that by downgrading to firmware 3.0 your 3G[S] will still have the 3.1 baseband and may not be unlockable in the future.