The Ultrasn0w 1.2.1 is out now and you could use it to fix the signal bar issues after unlocking the iPhone. But Ultrasn0w 1.2.1 is not an unlock for the newer basebands, but instead, an unlock for the older basebands (given below). I’ve explained here how to unlock iPhone 3GS 4.3.1 iOS on supported basebands.

Supported basebands for iPhone 3GS – 04.26.08, 05.11.07, 05.12.01, 05.13.04, 06.15.00

How to Unlock iPhone 3GS iOS 4.3.1

1. Jailbreak your iPhone 3GS 4.3.1 iOS using Sn0wbreeze on Windows or PwnageTool on Mac.

Guide: How to Use Sn0wbreeze 2.5 (Just use Sn0wbreeze 2.5.1 instead of 2.5)

Guide: How to Use PwnageTool 4.3

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 :

Unlock iPhone 3GS 4.3.1 iOS

6. The search for ” Ultrasn0w 1.2.1 ” in Cydia.

Unlock iPhone 3GS 4.3.1 iOS

7. Install the app.

8. Reboot your iPhone 3GS.

Unlock iPhone 3GS 4.3.1 iOS

That’s it! You’ve unlocked iPhone 3GS on iOS 4.3.1.

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