The following is a guide to unlock iPhone 3GS on iOS 5.0.1 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 latest redsn0w for Windows / Mac
- Start redsn0w. Go to Extras->Pwned DFU and follow instructions to get the iPhone in Pwned DFU mode.
- Start iTunes. Shift+Click Restore and choose the file downloaded in step #1
- If your phone is on old boot rom, skip this step. Otherwise, Power off the phone. Start redsn0w. Choose Jailbreak and follow instructions to jailbreak the phone. uncheck install Cydia.
- Reboot the iPhone. Enter Cydia and search for Ultrasn0w package. Install it.
- Turn off and then turn on airplane mode. Voila! Your iPhone 3GS is unlocked on iOS 5.0.1!
Did it work for you? Please leave a comment!