iOS 4.3.1 unlock is now possible by using Ultrasnow and Ultrasn0w Fixer on iPhone 4 and iPhone 3GS. It is to be noted that Ultrasn0w and Ultrasn0w Fixer work on certain basebands only.
Find more details about how and which basebands (Modem Firmware) can be unlocked on iOS 4.3.1 after the break.
- Ultrasn0w now works for basebands (01.59.00 / 04.26.08 / 05.11.07 / 05.12.01 / 05.13.04 / 06.15.00)
- Ultrasn0w is NOT compatible with the folllowing basebands! (02.10.04 / 03.10.01 / 04.10.01 / 05.14.02 / 05.15.04)
It is very important that you restore to custom iOS 4.3.1 while preserving the baseband so that you don’t loose the unlock ability. For this purpose you can user Sn0wbreeze 2.5 (Windows only) or PwnageTool 4.3 (Mac Only) which not only preserves the baseband but also provides untethered jailbreak during building a custom iOS 4.3.1.
Here is the step by step guide to unlock iOS 4.3.1 on iPhone 4 and iPhone 3GS provided you are still on unlockable baseband.
Step 1: Backup your device using latest version of iTunes before starting the actual process.
Step 3: Once your device is jailbroken, connect it with internet using a WiFi connection.
Step 4: Launch Cydia from your device Springboard.
Step 5: Tap on Manage and select “Sources“.
Step 6: Touch on “Edit” and then on “Add“.
Step 7: You will be prompted to add the source URL http://repo666.ultrasn0w.com(its zero in Ultrasn0w) as shown in the image below.
Step 8: After the source has been added, use the Search option and type Ultrasn0w to search and install it.
Step 9: Restart iPhone after installing Ultrasn0w. Because the current version of Ultrasn0w is still broken on iOS 4.3.1, so you have to install Ultrasn0w Fixer.
Step 10: Now add this source in the same way as you did above http://cydia.pushfix.info
Step 11: Search for Ultrasn0w Fixer using the search option.
Step 12: Tap on Ultrasn0w Fixer and press “Install” option.
After installing this fixer you will see the carrier name and signal bars in the top left corner.
This guide is posted for testing and educational purposes only. Please don’t try it if you don’t know what you are going to do. We won’t be responsible for any type of damage. [thanks @pushfix and msft.guy]