How to Downgrade Baseband 5.15.04 with Fuzzyband 4.1

Note: This tutorial works only for iPhone 3G.

Did you upgrade to iOS 4.2 and found out that your baseband is on version 5.15.04? Currently, there is no software unlock available.

Fuzzyband version 4.1 is out on Cydia. It will downgrade baseband version 5.15.04 to 5.13.04 for Ultrasn0w.

However, this only works for iPhone 3G with bootloader version 5.08.

How to downgrade your baseband from 5.15.04 to 5.13.04:

1. Launch Cydia from your springboard, and go to systems under section tab.

2. Press to select 3G Fuzzyband Downgrader from the list of packages and click on install.

3. After installation is completed successfully return to Cydia and press home button and launch Fuzzyband.

4. A message will be displayed if your bootloader is not supported, If you have the 5.08 bootloader you will be able to downgrade from baseband 05.15.02. Press the Downgrade button to begin downgrading your baseband.

5. Once the downgrade has completed successfully you will be displayed a Done! message saying, “I Haz Downgrade!”

You can quickly check your bootloader version by using TinyUmbrella. Download it from here. It should show your bootloader version right away.

Alternatively, you can also try using f0recast [Windows or Mac]. If you have bootloader 5.8, you will see the prompt below:

Lets start!

What you need:

1. Jailbroken iPhone 3G
2. Fuzzyband – install this from Cydia
3. afc2add – install this from Cydia although not necessary
4. i-Funbox – a file explorer for iPhone, Mac users can use DiskAid
5. 5.15.04 certificate (download ICE2-05.15.04.cert) for Fuzzyband

Steps:

1. Launch Fuzzyband after installing the app via Cydia.
2. Connect your iPhone to the computer.
3. Launch i-FunBox and select File, then go to Applications/Fuzzyband.app, right-click and then select Copy from PC.
4. Copy ICE2-05.15.04.cert you have downloaded earlier to this location
5. Go back to Fuzzyband and you can now begin the downgrade process. If the downgrade is successful, you should see “I Haz Downgrade“
6. You can now unlock it with ultrasn0w.