Ultrasn0w fixer for.2 has been released to make ultrasn0w 1.2.1 work with .2 to and with old basebands.
Take a serious look below and find your basebands
01.59.00 / 04.26.08 / 05.11.07 / 05.12.01 / 05.13.04 / 06.15.00
Unsupported basebands :
02.10.04 / 03.10.01 / 04.10.01 / 05.14.02 / 05.15.04 / 05.16.02
You have to jailbreak your on 6.15.00 basebands on 4.1 / 4.2.1, you can follow for or guide for Windows / (You may lose your GPS)
Take step by step to unlocking below…
Step 1: Now you have to jailbreak your 4 or iPhone 3GS on the latest 4.3.2, you can follow this guide ( with Sn0wbreeze 2.6 for Windows) or this guide (Tethered with for Mac)
Step 2: Open on your iPhone 4 or 3GS
Step 3: Go to Manage->Sources
Step 4: Now tap on “Edit”, then tap on “Add” and Enter the following repo http://djayb6.com
Step 5: Now tap on “Add Source” then tap on Done.
Step 6: Search for “ultrasn0w fixer for 4.3.2” inand install this application. This app will automatically your iPhone so that you can use it with any carrier.
Step 7: Now simply restart your iPhone and you should now have a fully unlocked iPhone 4 or 3GS, running iOS 4.3.2.