How To Unlock iOS 4.3.1 on iPhone 4, 3GS Using Ultrasn0w 1.2.1? [Guide]

by Jawwad in Guides, iPhone, Mobile | 1 comment

iPhone 3GS Unlock | How To Unlock iOS 4.3.1 on iPhone 4, 3GS Using Ultrasn0w 1.2.1? [Guide]

After some waiting iPhone Dev team has finally released the latest  Ultrasn0w 1.2.1. It was required because the current version of the Ultrasn0w 1.2 was broken on the latest iOS 4.3.1. This version also fixes signal bar issues. It should be emphasized again that this is NOT a new unlock for the new basebands but it fixes the issues on already compatible basebands namely: 01.59.00 / 04.26.08 / 05.11.07 / 05.12.01 / 05.13.04 / 06.15.00.

Here is the change log from the developer:

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.

Here is a guide of unlocking the iOS 4.3.1 on iPhone 3GS and iPhone 4 using the Ultrasn0w 1.2.1 after untethered jailbreaking iOS 4.3.1 using PwnageTool 4.3 (on Mac) or Sn0wbreeze 2.5 (on Windows).

Before we proceed any further please make sure you understand the following points:

            • Ultrasn0w 1.2.1 supports unlock 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 following basebands (02.10.04 / 03.10.01 / 04.10.01 / 05.14.02 / 05.15.04).
            • Upgrading iPhone 3GS baseband to the 06.15.00 iPad baseband hack to unlock MAY cause you to lose your GPS!

iPhone 3GS Users: Update iPhone 3GS to 06.15.00 Baseband for Unlock:
iPhone 3GS is required to be jailbroken with 06.15.00 baseband for Ultrasn0w 1.2.1 unlock . Follow the complete guide posted here to update your iPhone 3GS baseband to 06.15.00 and jailbreak it on iOS 4.2.1 before proceeding further.

Now we move to the actual process:

Step 1: First you need to be jailbroken on iOS 4.3.1. Follow our guides to do untethered jailbreaking iOS 4.3.1 using PwnageTool 4.3 (on Mac) or Sn0wbreeze 2.5 (on Windows).

Step 2: Now you are jailbroken on iOS 4.3.1 you need to unlock the phone using the Ultrasn0w.

  • Load Cydia on your iPhone.
  • Push the Manage tab at the bottom.
  • Now push on the Sources.

iPhone4Unlock11 | How To Unlock iOS 4.3.1 on iPhone 4, 3GS Using Ultrasn0w 1.2.1? [Guide]

Step 3: Now tap on the Edit and then tap on Add. Now you will get a prompt to enter a URL source (see the screenshot below). Type the and tap on Add Source to add this repo if you haven’t already.

iPhone4Unlock21 | How To Unlock iOS 4.3.1 on iPhone 4, 3GS Using Ultrasn0w 1.2.1? [Guide]

Step 4: Cydia will now automatically update your sources by following a series of automated steps. When the installation is complete search for “ultrasn0w 1.2.1” in Cydia, and install it. It will automatically unlock your iPhone so that you can use it with any carrier without any further action.

Step 5: Finally restart you iPhone and you should now have a completely unlocked iPhone 4 or 3GS, running iOS 4.3.1!

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  • http://Iphone4wontactivatewithat&t Bolu

    I have jailbroken my iphone using the guides above however, when i inserted an at&t sim to activate it it keeps saying waiting….
    It did not activate and i need it to work with my T mobile sim card as well which is prepaid but with data plan.

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