Few days back, I have informed about the news from the iPhone Dev-Team about their new unlocking tool for the iOS 4.2.1 and 4.1 firmwares. As promised, the iPhone Dev-Team released this new tool called “Ultrasn0w 1.2” which will help you to unlock the new iOS versions on 3GS and 3G on basebands later than 05.13.04. iPhone 4 is using a new baseband this “Ultrasn0w 1.2” unlock tool will not work on that.
Follow the step-by-step tutorial given below to unlock your iPhone 3GS and 3G devices on iOS 4.2.1 / 4.1.
How To Unlock iPhone 3GS and 3G on iOS 4.2.1 / 4.1 with Ultrasn0w 1.2
1. The “Ultrasn0w 1.2” unlock tool requires 06.15.00 on your 3GS and 3G devices to go ahead with the unlock. So just follow this tutorial on how to upgrade your baseband to 06.15.00 using PwangeTool 4.1.3 so that you can update your iPhone 3GS or 3G baseband to 06.15.00 and jailbreak it on iOS 4.1 / 4.2.1.
2. Once you have done that Launch ‘Cydia’ on your jailbroken iPhone 3GS / 3G.
3. Click on the ‘Manage’ tab visible at the bottom of your iPhone screen and then click on the ‘Sources’ button which appears on the screen as shown in the screenshot below.

4. Now click on the ‘Edit’ button from the top and then click on the ‘Add’ button which appears. Once you do that, a prompt will open up on your screen asking you to enter the url source. Just enter “repo666.ultrasn0w.com” in the space and click ‘Add Source’ button as shown in the screenshot below.

5. The sources will be automatically updated by Cydia software and once the process is over click on ‘Return to Cydia’ button and then click ‘Done’.
6. Now select the “repo666.ultrasn0w.com” url from the list of sources and select ultrasn0w to install and then confirm it by clicking ‘Confirm’ to start the installation.
7. Once “Ultrasn0w 1.2” is installed, this app will automatically unlock your iPhone so that you can use it with any carrier. Now just reboot the iPhone to finish the process.

That’s it. Now you have an unlock iPhone 3GS / 3G running on iOS 4.2.1.
If you encounter any difficulty while following this tutorial, do let us know here using the comments section. We will get back to you ASAP and we will help you to fix the issue.
For Further Reading:
- How To Update iPhone 3GS / 3G Baseband to 06.15.00 with PwnageTool 4.1.3 for iOS 4.2.1 Unlock
- Jailbreak and Unlock the IPhone 4, IPhone 3Gs And IPhone 3G Running 4.1 iOS with iPhone Unlocking Software
- How To Jailbreak iOS 4.2.1 GM on iPhone 4, 3GS, 3G and iPod touch 4G, 3G with Redsn0w 0.9.6b2?
- How To Put Your PC Monitor To Sleep Mode Using iPhone?
- How to Track your iPhone, iPad or iPod touch on iOS 4.2.1 With Find My iPhone for Free
- Download iOS 4.2.1 GM for iPhone 4, 3GS, iPad, iPod Touch and SDK
- How To Jailbreak iOS 4.2.1 using Updated Redsn0w 0.9.6b4
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