Guide: How to Unlock iPhone 4/ iPhone 3GS on iOS 4.3.1 with Ultrasn0w 1.2.1 [Download]

As we have earlier told you that iPhone Dev Team is going to release the new version of Ultrasn0w to Unlock iPhone 4 and iPhone 3GS. So you can now Use Ultrasn0w 1.2.1, this new update brings support to iOS 4.3.1 and fix the signal bar issue on iPhone 4. Users should keep in mind that, there's nothing new here this unlock is for all those older basebands which were already Unlockable i.e 01.59.00 / 04.26.08 / 05.11.07 / 05.12.01 / 05.13.04 / 06.15.00.

Note: iPhone 4/3GS users on Baseband 05.14.02, 05.15.04, 05.15.04, 05.16.01 & 05.16.02, 2.10.04, 03.10.01, 04.10.01.can't be unlock until now, Dev Team is working on the Unlock and as soon as it's completed we'll inform you.

According to iPhone Dev Team:

We’ve pushed out the 4.3.1 compatibility fix for ultrasn0w in Cydia — it’s now at version 1.2.1.  If you’re not already at 4.3.1 and you need the unlock, please be sure you understand how to get to 4.3.1 using a custom IPSW that doesn’t update your baseband.
This isn’t a new unlock! It’s to allow those who are already unlocked to use FW 4.3.1.  It also fixes the signal bar issue for those who aren’t using the unlock but retain an older baseband intentionally.

AFTER INSTALLING ULTRASN0W 1.2.1, PLEASE REBOOT YOUR iPHONE using the normal “slide to power off” swipe.  T-Mobile users in the USA also should disable 3G mode in Settings->General->Network.

A big thanks to @sbingner and @ronaldsb for helping with the testing of this update!

You have to make sure that your iPhone 3GS running on BB 05.14.02  or 05.15.04 should be Updated to 06.15.00. If it's not then just follow here to do so.

So before staring the Unlock you have to Make sure your iPhone is Jailbroken on iOS 4.3.1. If it's not then follow our Guide here to Untethered Jailbreak it with Redsn0w on Windows [or] Jailbreak it with Pwnage Tool on Mac.

Guide: How to Unlock iPhone 4, iPhone 3GS running iOS 4.3.1 with Ultrasn0w 1.2.1, old baseband:

Step 1: First of all Go to "Cydia" then "Manage Tab"

Step 2: Now Go to "Sources" then Click "Edit" and click "Add"

Step 3: Now Write,

http://repo666.ultrasn0w.com

And then click "Add Source"

Step 4: Once the Repo has been added, Just search for "Ultrasn0w" in Cydia and Install it.

Step 5: Click Install, And then Restart your iPhone.

Congratulations, It's Unlocked!

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