If your iPhone 4 is on 01.59.00 baseband, then you are lucky. Ultrasn0w 1.2.1 could unlock it on iOS 4.3.1. Then some of you will be thinking why we can’t unlock it with Ultrasn0w 1.2 instead of 1.2.1. The newer version of Ultrasn0w was released in order to fix the signal bar issue after unlocking. If you use the previous version, you can’t find any signal bar on your phone.
Now, let’s proceed to the work of unlocking iPhone 4 on iOS 4.3.1 :
1. Jailbreak your iPhone 4 on 4.3.1 iOS using Sn0wbreeze on Windows or PwnageTool on Mac.
2. Open up Cydia.
3. Select the Manage tab at the bottom.
4. Tap on the edit button and then on the add button.
5. Then add this repo : http://repo666.ultrasn0w.com.
6. The search for ” Ultrasn0w 1.2.1 ” in Cydia.
7. Install the app.
8. Reboot your iPhone.
That’s it! You’ve unlocked iPhone 4 on iOS 4.3.1.
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