How To Downgrade iPhone 3G Firmware 4.0 Baseband 05.13.03 To Baseband 04.26.08

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Fuzzyband Downgrader, the Cydia app that allows you to downgrade your iPhone firmware, has been updated for the latest baseband 05.13.03 of iPhone OS 4 Beta. Similar to the previous version, this one also lets you downgrade your iPhone 3G (doesn’t work with 3GS) for older boot loader 05.08.

Here are the steps to downgrade iPhone OS 4.0 baseband 05.13.03 to baseband 04.26.08:

1. First jailbreak your iPhone 3G OS 4.0 using redsn0w 0.9.5.

2. Launch ‘Cydia’, go to ‘Sections’ –> ‘System’.

3. Search for ‘Fuzzyband Downgrader’ and install the application.

4. Launch Fuzzyband Downgrader app, which will then query your iPhone’s modem to retrieve details such as bootloader version, baseband version, and OS version.

5. If your phone’s bootloader is 05.08, you can then tap on ‘Downgrade’ to start the downgrading process.

After downgrade is completed, you can unlock your iPhone 3G OS 4.0 using Ultrasn0w.

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