The iPhone Dev team have released a special edition PwnageTool (v4.1.3) which can update the baseband of iPhone 3GS & 3G to 06.15.00 so that they can be unlocked using Ultrasn0w 1.2 on the latest iOS 4.2.1 (or iOS 4.1) firmware. As you might already know, basebands 05.14.xx and 05.15.xx are currently unlockable and hence this update becomes necessary.
Risks involved
Please read and understand the following risks involved before proceeding with the update.
There is no way to come back down from 06.15, and there’s no hiding the baseband version from Apple. You’ll be voiding your warranty in a very obvious way. If some future baseband comes out with a critical fix, you won’t be able to update to it if it remains down in the 05.xx sequence (then again, you wouldn’t update to it if you wanted to keep your unlock anyway). Starting with FW 4.2.1 if you have 06.15 on your iPhone you won’t ever be able to restore to stock firmware (it will fail). You’ll need to only restore to custom IPSWs (then again, if you’re unlocker you should already be doing that).
Now if you still want to proceed with the baseband update, follow the guide given below at your own risk. Step 1: Download iPad 3.2.2 firmware file (Required for 06.15.00 baseband). Step 2: Download the required iOS 4.2.1 or iOS 4.1 firmware file. Step 3: Download PwnageTool 4.1.3 from here. Step 4: Start PwnageTool 4.1.3 and point it to iOS 4.2.1 / 4.1 firmware file. Step 5: You will now be prompted to update your baseband to 06.15.00 so that it can be unlocked using Ultrasn0w 1.2. Step 6: Now point PwnageTool 4.1.3 to iOS 3.2.2 for iPad. PwnageTool will fetch the exploitable 06.15.00 baseband from 3.2.2 firmware and will replace it the baseband in iOS 4.2.1 / 4.1. Step 7: Click the next arrow to allow PwnageTool to create this custom ipsw file for you. Step 8: Now enter the DFU mode. Step 9: You will now have to restore your iPhone to this custom firmware 4.2.1 / 4.1 file. For this, start iTunes, click on your device icon from the sidebar in iTunes. Now press and hold left “alt” button (“Shift” button on Windows) on the keyboard and then click on “Restore” (Not “Update” or “Check for Update”) button in the iTunes and then release the “Shift” button. This will make iTunes prompt you to select the location for your custom firmware 4.2.1 / 4.1 file. Select the required custom .ipsw file and click on “Open”. Step 10: A series of automated steps will follow this. Just wait while iTunes installs the new firmware 4.2.1 / 4.1 on your iPhone 3GS or 3G. After the installation is done, your iPhone will restart automatically and you should now have a fully jailbroken iPhone 3GS or 3G with 06.15.00 baseband. A guide to unlock iOS 4.2.1 will follow next. [via]Redmondpie
