DevTeam has finally rolled-out ultrasn0w 1.2 to unlock iPhone 3GS and iPhone 3G on iOS 4.1. Notably, baseband 05.14.02 and 05.15.04 are still locked and you need to update your iPhone 3GS or 3G to baseband 06.15.00 using PwnageTool 4.1.3.
How to Unlock iPhone 3GS, 3G on iOS 4.1 / 4.2.1 with Ultrasn0w
Step 1 - Jailbreak iPhone 3GS or iPhone 3G on iOS 4.1 or iOS 4.2.1 using pwnageTool 4.1.3 to update to Baseband 06.15.00. (Follow Guide posted here)
Step-2 - Start ‘Cydia’ on your jailbroken iPhone iOS 4.1 or iOS 4.2.1 springboard.
Step 3 - Select ‘Manage’ tab at the bottom of your iPhone screen and then select ‘Sources’.
Step 4 - Select ‘Edit’ and then select ‘Add’. Now enter a URL source. Type ‘repo666.ultrasn0w.com‘ and select on ‘Add Source’. Once Cydia has added the source click on ‘Return to Cydia’ button.
Step 5 - Once the installation is completed. Search for ‘ultrasn0w’ in Cydia and install it.
Step 6 - This will automatically unlock your jailbroken iPhone 3GS, 3G running baseband 06.15.00.
Step 7 - Reboot it.
Voila! You have now successfully unlocked iPhone 3GS, 3G iOS 4.1 and iOS 4.2.1 firmware. For all future jailbreak and unlock software releases, please follow us on Twitter or become a Facebook fan. You may also like to check out more on iPhone Jailbreak and iPhone unlock.