Yes, you read that right. Now you can downgrade the “Modem Firmware” or “Baseband” of your iPhone 3G from 06.15.00 to 05.13.xx, which is also unlockable using Ultrasn0w unlocking tool. By downgrading the baseband, you will also be able to restore your device to the official stock firmware using iTunes, which was not possible on baseband 06.15.00.
The complete how-to guide to downgrade your iPhone 3G baseband to 05.13.xx is written below. Currently this guide will only work for iPhone 3G with bootloader 5.8.
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Important Note: Follow the guide on your own risk. We recommended you to make a complete backup of all the data stored on your iPhone before proceeding with the below guide.
Requirement for Downgrading iPhone Baseband to 05.13.xx
Below is the list of things you will need:
- Jailbroken iPhone 3G.
- Fuzzyband installed on your iPhone via Cydia.
- afc2add installed on your iPhone via Cydia.
- If you’re on Windows then download i-FunBox from here, OR if you’re on Mac then download DiskAid from here.
- Certificate for use with Fuzzyband (download link in Step 4).
How to: Downgrade iPhone 3G Baseband to 05.13.xx
Step 1: Install Fuzzyband on your iPhone through Cydia.
NOTE: (It is important to verify that Fuzzyband should say you that your bootloader is 5.8, incase if not, then do not proceed further).
Step 2: Connect your iPhone 3G to Computer via USB.
Step 3: Start “i-FunBox” or “DiskAid” and click “File” then navigate to “Applications/Fuzzyband.app”, right-click and then select “Copy” from PC.
Step 4: Download the “ICE2-06.15.00.cert” file from here and then “Move” or “Copy” it to this location: “Applications/Fuzzyband.app”.
Step 5: Now simply disconnect your iPhone from your computer and start “Fuzzyband” app on your iPhone.
Step 6: In Fuzzyband, you will see your current version of Baseband, (which should still be 06.15.00) and you will also have the option to downgrade the baseband to version 05.13.xx. So just downgrade it.
Once you have downgraded the baseband, you can check and confirm it by going to “Settings” -> “About” and then scroll down to see your “Modem Firmware” or “Baseband” which should now be 05.13.xx.
The baseband 05.13.xx is unlockable using Ultrasn0w unlocking tool, the how-to guide for which is posted by us here. Now you can also update or restore any firmware of your iPhone using iTunes without any error.