How to unlock iPhone 3G on iOS 4.2.1 with baseband 05.15.04
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ljhurt • October 2, 2012 at 2:50pm
How can I unlock an iPhone 3G running iOS 4.2.1 with baseband 05.15.04? I successfully jailbroke the device, but I am receiving a bzip2 error code (2) when trying to install ultraSn0w from the repo666.ultrasnow.com repository in Cydia. Is there a specific process I need to follow to fix this error and unlock the phone?
Answers
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iClarified • January 11, 2026 at 8:40pm
To unlock an iPhone 3G on iOS 4.2.1 with baseband 05.15.04, you must first change the baseband because 05.15.04 is not compatible with the ultraSn0w unlock tool. The standard method involves using redsn0w to update your device to the iPad baseband (06.15.00) and then downgrading it to 05.13.04, which is unlockable.
1. Download the version of redsn0w compatible with your computer and the iOS 4.2.1 IPSW file for iPhone 3G.
2. Open redsn0w, select your IPSW, and choose the option to Install iPad baseband. Be aware that this process carries a small risk of hardware failure for certain serial numbers and can affect GPS functionality.
3. Once the update is finished, run redsn0w again and select the option to Downgrade from iPad baseband. This will bring your baseband to version 05.13.04.
4. After the downgrade is complete, open Cydia and install ultraSn0w. If you still encounter repository errors, the servers for repo666 may be offline due to the age of the device, and you may need to manually install the ultraSn0w deb file using a file manager like iFunBox or via SSH.
1. Download the version of redsn0w compatible with your computer and the iOS 4.2.1 IPSW file for iPhone 3G.
2. Open redsn0w, select your IPSW, and choose the option to Install iPad baseband. Be aware that this process carries a small risk of hardware failure for certain serial numbers and can affect GPS functionality.
3. Once the update is finished, run redsn0w again and select the option to Downgrade from iPad baseband. This will bring your baseband to version 05.13.04.
4. After the downgrade is complete, open Cydia and install ultraSn0w. If you still encounter repository errors, the servers for repo666 may be offline due to the age of the device, and you may need to manually install the ultraSn0w deb file using a file manager like iFunBox or via SSH.
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VBee • October 3, 2012 at 6:35am
The bzip2 error often occurs when a connection to the repository is interrupted, but your primary obstacle is that baseband 05.15.04 cannot be unlocked directly. To proceed, you must use redsn0w to update to the iPad baseband and then immediately downgrade to baseband 05.13.04. Once your baseband is 05.13.04, you can install ultraSn0w from Cydia to unlock the device for use with other carriers.