The following is a guide to unlock iPhone 3GS on iOS 5.1.1 via software. Before you proceed, please make sure that your iPhone 3GS is not one of the ones that comes with Toshiba baseband chip. This is the easiest/fastest method i've found and i've tested it working personally. The risk of bricking your phone is minimal.
- Check the serial number of your iPhone, if it's produced before 41th week of 2009 (old boot rom), it's on old bootrom and you need to download this file. Otherwise (new boot rom), you need to download this file. If you do not know which week it is produced, you can use this tool to check.
- Download Official iPhone 3GS iOS 5.1.1 firmware from Apple.
- Download latest Sn0wbreeze for Windows.
- Start Sn0wbreeze, choose your bootrom type from #1 and select expert mode.
- Choose install iPad baseband.
- Click Build IPSW and a custom firmware will be saved on your desktop.
- Follow instructions in Sn0wbreeze to put the phone in pwned DFU mode.
- Start iTunes. Shift+Click restore in iTunes and choose the custom firmware you just build. iTunes will start restoring firmware onto the iPhone.
- Once the restore is complete. iPhone will reboot.
- Start Cydia on iPhone. Wait for it to finish loading.
- Search for Ultrasn0w and install it in Cydia.
- Reboot the iPhone. Congratuations, your iPhone 3GS is now unlocked.
Did it work for you? Please leave a comment!