How to Downgrade Your iPhone 3G 2.30 (2.2.1) Baseband for Unlock

These are instructions on how to downgrade your baseband from 2.30 to 2.28 for iPhone 3Gs with the 5.8 bootloader. This will allow you to unlock your iPhone 3G using YellowSn0w. An similar exploit is still be worked on for those with a higher bootloader version...

IMPORTANT: Make sure your iPhone uses the 5.8 bootloader before continuing. You can find instructions on how to check your bootloader version here: Windows, Mac. Ensure you are on the 2.30 baseband by following this tutorial. You will also need MobileTerminal installed to completed this tutorial.


Step One
Launch Cydia by pressings its icon on your SpringBoard.


Step Two
Press to select the Manage tab at the bottom of the screen.


Step Three
Press to the large Sources button.


Step Four
Press the Edit button at the top right of the screen.


Step Five
Press the Add button at the top right of the screen.


Step Six
Enter http://nakedproductions.us/source as the source address and press the Add Source button.


Step Seven
Press the Return to Cydia button once the source has been loaded.


Step Eight
Press the Done button.


Step Nine
Press to select Naked Productions from the list of sources.


Step Ten
Press to select DownBB from the list of Packages.


Step Eleven
Press the Install button at the top right of the screen.


Step Twelve
Press the Confirm button to begin installation.


Step Thirteen
Once installation has completed successfully press the large Return to Cydia button.


Step Fourteen
Press the Home button to return to your SpringBoard then press to launch Terminal


Step Fifteen
Enter su into the terminal window then enter alpine when prompted for a password.


Step Sixteen
Enter DownBB into the terminal window to launch the baseband downgrade script.


Step Seventeen
You will be asked to confirm you would like to continue. Please make sure you are on the 2.30 baseband and have the 5.8 bootloader before entering yes into the window.


Step Eighteen
DownBB will now execute the script which downgrades your baseband.


Step Nineteen
Once the script has completed please restart your iPhone and take note that you are now on the 2.28 baseband.


Step Twenty
You may now unlock your iPhone using the iPhone 3G unlock tutorial found here!



THANKS
Many thanks to EvilPenguin|, pH, and DHowett for their work on this script!