Note that this tutorial was originally written for the 3.0 unlock but the steps are exactly the same to unlock iPhone OS 3.0.1. I simply updated this guide with the latest info.
Before installing UltraSn0w, your iPhone 3G has to be jailbroken and running the latest 3.0 3.0.1 firmware. You can either jailbreak your iPhone 3G using RedSn0w (see tutorial here) or by using PwnageTool (see tutorial here).
After jailbreaking your iPhone 3G, follow these simple steps:
- Launch Cydia.
- Add the following source to Cydia repo666.ultrasn0w.com (note there is a “0″ in sn0w, not an “o”).
- After installing this source in Cydia, search for “ultraSn0w”.
- Install UltraSn0w and reboot your iPhone.
Note that T-Mobile users should disable 3G before using UltraSn0w.
Unfortunately, the new iPhone 3G S still can’t be unlocked because there is no jailbreak for it yet.