How to update iPhone baseband to 06.15.00 for unlocking on iOS5
Alright, so it has come to my attention that many of our readers have an iPhone3Gs and would like to unlock their phones but are on a baseband which is not unlockable. The good news about the iPhone3Gs is that no matter what baseband you have, you can use Redsn0w to update your baseband to the iPad baseband, 06.15.00 which IS unlockable with Ultrasn0w 1.2.4 on iOS5.
*WARNING* By updating your iPhone to the 06.15.00 baseband you run a HUGE risk of losing your GPS functionality. I would say probably 9/10 iPhones that use the 06.15.00 baseband lose their GPS, there is NO FIX for this and it is IMPOSSIBLE to downgrade your baseband once it's been upgraded. Also, by updating your baseband to 06.15.00 you will no longer be able to do a normal update or restore in iTunes. You MUST restore a custom firmware from here on out if you decide to update your baseband.
That being said, the last version of Redsn0w to support the iPad baseband option is Redsn0w 0.9.6rc16. This is because MuscleNerd and the iPhone-Dev team decided to stop adding the option to their software because of the issues it causes. Don't get me wrong, this WILL work no problem, but you will likely lose GPS and you will have to restore custom firmwares from here on out, but because the iPhone-Dev team are purists they opted to remove the option rather than to leave it and put a disclaimer.
Step 1: Download Redsn0w 0.9.6rc16 from above and open it. On the very first screen you will have to browse for your 4.3.3 IPSW file you downloaded above(remember it doesn't matter what firmware you are on, you must use a 4.3.3 IPSW).
Step 2: After Redsn0w has verified your firmware you will receive a notice that asks if you have the old or new bootrom version. If you don't know you can check with f0recast.
Step 3: Now, click next and you will be presented with the options screen. On this screen you want to select ONLY the "Install iPad Baseband" option. DO NOT select anything else.
Step 4: After selecting the iPad baseband option hit next. On the next screen you will be instructed on how to put your device into DFU mode. At this time you can go ahead and put your device into DFU mode if you know how to already, otherwise just hit next again and follow the onscreen instructions which will tell you how.
Step 5: Once Redsn0w detects your device in DFU mode it will begin to download and install the iPad baseband onto your phone. Once your phone reboots go into settings>general>about and check next to "modem firmware" to make sure that your baseband has successfully been updated to the iPad baseband. If it is then you can go ahead an unlock with Ultrasn0w 1.2.4!
Did you find this tutorial useful? If so, please consider donating below, thank you!