Here I show you how to update 05.16.05 to 06.15.00 to complete iOS 5.1 unlock on iPhone 3GS here. As there is no untethered jailbreak for iOS 5.1 jailbreak for will show you the method to unlock your 05.16.05 (which becomes here 06.15.00) baseband. Warrning: This baseband is the iPad baseband and can break your GPS. Note:It all can be done at your own risk. Read important info about risks of updating to iPad baseband 06.15.00.


How to update 05.16.05 to 06.15.00 Basebands

update 05.16.05 to 06.15.00 Note: Backup all your iPhone data files and remove Sim card. Step 1. Put your iPhone 3GS into the DFU mode: Hold down both the Power and Home buttons simultaneously for 10 seconds. Release the Power button but keep holding the Home button for 10 more seconds. If your screen is black, you’re in DFU mode. Step 2. Open iTunes, connect iPhone to the computer, hold down SHIFT for Win or OPTION for Mac and click RESTORE button in iTunes. Now you can release SHIFT/OPTION. Select iOS 4.1 that you just have downloaded. If you receive 3194 error in iTunes that use this link to fix it. Step 3. Restore process will end with 1015 error and recovery loop on the iPhone. You can fix it by using Exit Recovery button in TinyUmbrella (that is why you have downloaded it). Step 4. Launch RedSn0w 0.9.8rc18. Step 5. Now select Install Cydia and Install iPad Baseband. Note: Installing iPad baseband will break your GPS. Step 6. Now follow on screen instructions and put your device in to the DFU mode and begin jailbreaking process and complete it. Step 7. After that you will have jailbroken iPhone 3GS on iOS 4.1 with iPad baseband 06.15.00. And that's it. Now your iPhone 3GS is on 06.15.00 running iOS 4.1. That is all you need to complete iOS 5.1 unlocking process on baseband 05.16.05.