It was only a few days ago that we brought you the exciting news that iPhone Dev Team and their rock star lead MuscleNerd had been working covertly on a way to allow users to downgrade the baseband on their iPhone 3G and 3GS from 06.15.00 to a prior one with full unlock and GPS support. This may not be something which some of you actually require, but for those unfortunate ones who had to update to the iPad baseband to get an unlock last year, it is certainly a nice welcome, especially with the launch of Apple’s new Maps service in iOS 6 that makes extensive use of the device’s GPS capabilities.
With all dev teams and researchers dedicating their time to tinkering with the first beta of iOS 6, it looked as if the downgrade option would play second fiddle to producing an initial beta jailbreak, but thankfully one of the hardest working developers in the community has pushed out an update to the popular Redsn0w tool with an additional baseband downgrade option. If you happen to be one of the affected users who is looking for a reprieve from the 06.15.00 baseband limitations then salvation has come.
Note: Before you begin, it’s necessary to note that this method will only work on devices which are running the 06.15.00 baseband; namely, the iPhone 3GS and the iPhone 3G. This guide does not apply to iPhone 4 nor iPhone 4S users. Make sure to backup your device in case anything goes wrong during the process. It’s best you read the guide in it’s entirety before going ahead with it.
And also, here’s a big warning from the iPhone Dev Team themselves for iPhone 3GS users running the latest bootrom:
If you have an iPhone3GS and if digits 3-5 of its Serial Number are 134 or later (xx134…), then you should NOT try to install the 06.15 baseband on your 3GS! It will brick your radio, preventing both the downgrade from working and normal iPhone software from using it as a phone! Be warned!
Step 2: Unzip the contents of the downloaded compressed file and save to a familiar location on your PC or Mac.
Step 3: Download the IPSW file of iOS which is currently running on your device, use the search bar on the right-hand side of this post to hunt for the required files. Once downloaded and saved to a safe location, move to the next step.
You can check which version of iOS you are running by going to Settings > General > About > Version.
Step 4: Launch Redsn0w and click on the Extras button on screen.
Step 5: Now click on the Select IPSW option. Point Redsn0w towards the IPSW file which you downloaded in Step 3. If you’re already running iOS 5.1.1, then point it towards that said firmware and so on. Click on Open when you’ve found the required IPSW.
Step 6: Redsn0w will now ask you whether if you have an older bootrom iPhone 3GS or a new one, read the on-screen instructions very, very carefully before you proceed, as it may potentially lead to the loss of data on your device, or may even brick your device’s radio for good.
Step 7: Now go back to the main screen of Redsn0w and click on the Jailbreak option. After preparing the jailbreak data – which takes a little while – you will be presented to a set of different options.
Step 8: Simply check the Downgrade from iPad baseband and Install Cydia options and click Next. If you’re already jailbroken and have Cydia installed then you do not have to check the Install Cydia option.
Step 9: At this point, make sure your device is powered off and unplugged. Read the on-screen instructions on how to put your device in DFU mode, don’t worry it might take a couple of tries to get it right. Once you’re ready, click Next.
Step 10: When you’re into DFU mode, Redsn0w will do it’s thing and proceed with the downgrade of your baseband, don’t be alarmed as this step might take a while, so be patient. And best of all; do not touch your device during the whole downgrade process.
Step 11: If you followed the steps correctly, your iPhone will reboot and will be on the unlockable 05.13.04 baseband. Simply launch Cydia and use the latest version of Ultrasn0w to unlock your device.
So there you have it, an unexpected but extremely welcome addition to the Redsn0w feature list. For those who are confused as to what baseband to actually downgrade to, MuscleNerd himself has specified that he believes 05.13.04 would be a very good choice thanks to the availability of of an Ultrasn0w unlock and fully functional GPS capabilities.