Many iPhone 4 and 3GS users know about UltraSn0w 1.2.5 unlock. This unlocking tool can unlock iOS 5.1 too and I decided to show you how to guide. A not long time ago I wrote you how to guide to unlock iOS 5.0.1 using ultrsn0w 1.2.5 unlock on iPhone 4. So if you need it then check it. But let’s talk about iOS 5.1 unlock. UltraSn0w 1.2.5 patch or fixer tool is an old version but it can unlock some basebands on iPhone 4,3GS:
  • 01.59.00
  • 04.26.08
  • 05.11.07
  • 05.13.01
  • 05.12.01
  • 06.15.00
Ulltrasn0w 1.2.5 unlock for iOS 5.1 was developed by the iPhone Dev Team and it brings native support for the iOS 5.1 filmware on iPhone 4 and 3GS. unlock iOS 5.1 Using Ultrasn0w 1.2.5 Before we start our unlock iOS 5.1 using ultrasn0w 1.2.5 I must advice T-Mobile USA users to do some easy steps: Go to settings>General>Network and switch “Enable 3G” to OFF. You have to disable 3G network before we start unltrasn0w unlock for iOS 5.1. Other thing that you must know is that you have to jailbreak your iPhone 4,3GS before unlocking process, because you need Cydia.

How to unlock iOS 5.1 Using Ultrasn0w 1.2.5 on your iPhone 4,3GS

1.    Run Cydia and tap Manage 2.    Go to sources unlock ios 5.1 using ultrasn0w 1.2.5 fixer 001 3.    Tap Edit and then tap Add button unlock ios 5.1 using ultrasn0w 1.2.5 fixer 005 4.    After you see the form to type url then type this: unlock ios 5.1 using ultrasn0w 1.2.5 fixer 002 and tap Add Source. Downloading process won’t be long and after it finishes return to Cydia and tap done. Then you can see ultrasn0w fixer in the list of sources so install it and move back to Cydia. 5.    Now you need to find ultrasn0w 1.2.5 in Cydia. Just type ultrasn0w in the Search form and pick ultrasn0w fixer for 5.1. unlock ios 5.1 using ultrasn0w 1.2.5 fixer 006 6.    After you find it, just install ultrasn0w 1.2.5 to unlock iOS 5.1. This process running automatically. unlock ios 5.1 using ultrasn0w 1.2.5 fixer 010 7.    And the last step you must do is to reboot your iPhone 4,3GS. To complete this unlock follow this link and finish it. After rebooting you can use any Sim card you want on your unlocked iPhone 4 and 3GS on iOS 5.1 using Ultrasn0w 1.2.5 fixer.