Users are now able to unlock iPhone 4.3 iOS using Ultrasn0w, as iH8sn0w has released Sn0wbreeze 2.3b4 which supports Ultrasn0w on iOS 4.3 after jailbreak. You could unlock iOS 4.3 on iPhone 3GS/4 (3GS old bootrom only) on specific basebands (given below) after jailbreaking it with Sn0wbreeze 2.3b4.
Things to remember before trying this :
1. If you are having iPhone 3GS, then only old bootrom users should do this.
2. iPhone 3GS users must update to iPad baseband along with jailbreaking it on iOS 4.2.1 before proceeding. Guide for that is given here.
3. Ultrasn0w now works for basebands (01.59.00 / 04.26.08 / 05.11.07 / 05.12.01 / 05.13.04 / 06.15.00)
4. Ultrasn0w is not compatible with the folllowing basebands (02.10.04 / 03.10.01 / 04.10.01 / 05.14.02 / 05.15.04)
5. Upgrading your iPhone 3GS baseband to the 06.15.00 iPad baseband hack to unlock may cause you to lose your GPS!
How to Unlock iPhone 3GS/4 iOS 4.3 Firmware
4. Now follow the steps given here (from step 4 onwards) to jailbreak iOS 4.3 on iPhone 3GS/4 (Just do according to what device you have using Sn0wbreeze 2.3b4).
5. Now, open Cydia on your iPhone.
6. Choose the ” Manage ” tab at the bottom.
7. Choose the ” Sources ” option.
8. Tap the ” Edit ” button and then on the ” Add ” button.
9. Then add the source ” http://repo666.ultrasn0w.com “ on your iPhone 3GS/4.
10. After it is added, search for ” ultrasn0w 1.2 ” in Cydia.
11. Now, install the Ultrasn0w 1.2 app to unlock iPhone 4.3 iOS.
That’s it! You have safely unlocked your iPhone 3GS/4 on iOS 4.3 firmware!