It’s now possible to unlock iPhone 05.15.04 baseband after the release of ultrasn0w 1.2 unlock for iOS 4.2.1 but with a tricky step.
This unlock works perfectly to unlock your iPhone with baseband 05.15.04 but with a different procedure which is bit tricky. If you want to be notified when the unlock for 4.2.1 directly without updating comes out subscribe our RSS feed , twitter or Facebook. You will get all the latest updates at all three the places.
To unlock your iPhone 3G / 3Gs with baseband 05.15.04 (iOS 4.2.1) you need to update your iPhone to iPad iOS 3.2.2 baseband 06.15.00 first. Click here to upgrade your iPhone baseband to 06.15.00 with PwnageTool or to upgrade iPhone baseband to 06.15.00 using redsn0w.
Once the firmware with baseband 05.15.04 has been upgraded to 06.15.00 baseband, you can unlock it by following the instructions at:
Unlock iPhone 3G, 3GS Baseband 05.14.02, 05.15.04, 06.15.00 with Ultrasn0w 1.2.
This will let you successfully unlock iPhone 05.15.04 baseband with iOS 4.2.1