Apple released iOS 5.1 firmware last month and just like iOS 5.0 firmware this update also brings baseband upgradation for iPhone, iPad and iPd touch. Many iPhone 3GS users updated their iPhone’s iOS firmware to iOS 5.1 without having the knowledge of fact that their baseband will also get update to 5.16.05 which is not unlockable. Before iOS 5.1 update iPhone 3GS users who updated iOS 5.0 firmware get baseband update to 5.16.05 but after some weeks solution came from iOS jailbreak community that iPhone 3GS locked on baseband 5.16.05 can be unlocked by patching iPad’s baseband 6.15.00 which is a unlockable baseband.
Similarly if you want to unlock your iPhone 3GS then it’s still possible to do it by updating baseband 5.16.05 to the baseband 6.15.00. Baseband 6.15.00 is an unlockable iPad’s baseband but it will break your GPS but now this issue has been solve by iPhone Devs team and iH8Sn0w.
Warning: (1) If your iPhone 3GS was manufactured after 25th week of 2011 then Do Not follow this guide or it will break your iPhone 3GS’ baseband chip. You can check manufacturing week of your iPhone 3GS by just entering iPhone’s serial number in this website. iPhone’s serial number can be found Settings>General>About.
(2) Sn0wbreeze works on Windows, so this guide only for Windows users and Mac users will have to downoad custom firmware or ready made firmware for this process.
Unlock iPhone 3GS Baseband 5.16.05 Running On iOS 5.1 Firmware:
Things you need to download first:
Step 1: Download and install Sn0wbreeze 2.9.3 and open it up. Click on the blue arrow at the bottom right corner and browse for the firmware you just downloaded from the above posted link. Also connect your iPhone 3GS with PC via USB cable.
Step 2: Sn0wbreeze will verify your iPhone 3GS’ iOS 5.1 IPSW and give you an option to choose your bootrom. If you don’t know whether your iPhone has Old Bootrom or New Bootrom you can just click “I don’t know or New Bootrom”.
Step 3: Now select Expert Mode from the new window. Sn0wbreeze will do some process and in the next window check Hacktivate (Activate iPhone) option for unlocking purpose.
Step 4: After this sn0wbreeze will ask you whether you want to patch iPad’s 6.15.00 baseband or not, CHECK this option and a warning window will pop that’s normal press “Ok” .
Step 5:Now click ‘Build IPSW’ and click on next button. Building iOS firmware will take some time so be patience.
Step 6: Now Sn0wbreeze will automatically cook you iOS firmware on your desktop. Before restoring, you need to ‘pawn’ DFU your iPhone to allow it to accept custom firmware. Otherwise, you will get error 1600. Follow this guide to enter your iDevice into pwned DFU mode.
To enter in DFU mode:
- Hold Power and Home buttons for 10 seconds
- Now release the Power button but continue holding the Home button for 10 more seconds
- You device should now be in DFU mode (black screen)
Mac users can download custom iOS 5.1 firmware for iPhone 3GS from here.
Restore iOS 5.1 Custom Firmware via iTunes:
Now you have to restore iOS 5.1 custom firmware via iTunes. Open up iTunes, click on your iOS device icon from the sidebar in iTunes. Now press and hold Left “Shift” button on the keyboard and then click on “Restore” (Not “Update” or “Check for Update”) button in iTunes and then release this button.After restore process your iPhone will boot up and you’re ready to unlock it once you’ve gone through the setup process. Just to be sure, go to Settings> General>About and check that your Modem Firmware (baseband) is 6.15.00.
Booting In Tethered Mode With RedSn0w: As we told you earlier this is tether jailbreak so you need to boot your device tethered.This can be done by iBooty or latest version of Redsn0w.
LaunchRedsn0w, select “Extras”, then”Just Boot” in order to boot your device tethered.
Follow on screen instruction to put your iDevice in DFU Mode and tethered boot.
Now your iPhone 3GS has successfully jailbroken on iOS 5.1 firmware with baseband 6.15.00. Now you just have to use Ultrasn0w fixer patch to unlock iPhone 3GS running on iOS 5.1 firmware. To use Ultrasn0w fixer follow this step by step guide postedhere Unlock iPhone 4 and iPhone 3GS With Ultrasn0w Fixer On iOS 5.1.