Anyway you can jailbreak your iOS 5.1 device, follow this tutorial to semi untethered jailbreak iOS 5.1 with Redsn0 0.9.10b6.
This ultrasn0w fixer for 5.1 is developed by msftguy and zmaster, and if you are interested to install this tweak you can add this repo url: http://repo.iparelhos.com. However keep in mind that this package does not support all modem baseband. Only the ones that are listed in the next paragraph.
Here is a list of the Supported Basebands:
- 01.59.00 (iPhone 4)
- 04.26.08 (iPhone 3GS)
- 05.11.07 (iPhone 3GS)
- 05.12.01 (iPhone 3GS)
- 05.13.04 (iPhone 3GS)
- 06.15.00 (iPhone 3GS)
How to Preserve Baseband of iPhone and Jailbreak iOS 5.1:
In order to unlock your jailbroken iOS 5.1 device, make sure you don't restore your device to update to iOS 5.1 IPSW, preserve your baseband using Redsn0w 0.9.10b6 version and then use the Custom IPSW option to create a NO_BB* version of 5.1 IPSW.
To do so, do the following.
1. Open Redsn0w and then choose "Extras" option, followed with choosing "Custom IPSW" and then place your iOS 5.1 file.
2. Now enter PWNED DFU mode, Extras >>> Pwned DFU and then restore the custom firmware from iTunes.
How to unlock iOS 5.1 using UltraSn0w Fixer for 5.1
Step 1: Open Cydia form your device homescreen.
Step 2: Navigate to the Manage > sources > click edit.
Step 3: Now tap on Add, and then enter a URL on the provided popup box
Followed with tap on ‘Add Source’.
Step 4: Sources will be loaded and will see the iParelhos repo after refresh. Tap on the repo and there you will see Ultrasn0w Fixer utility.
Step 5: Now it's time to install the Ultrasn0w Fixer utility.
Step 6: Once installed, you can continue to install ultrasn0w 1.2.5.
Step 7: Reboot the device, once it's rebooted and turn it on you will notice that your iPhone should be unlocked on latest iOS 5.1 IPSW.