As you know Apple dropped iOS 4.0.1 for iPhone 3G, 3GS and iPhone 4 in response to wrong signal calculation. This is a minor update and no major changes in baseband update and jailbreak protection in comparison with iOS 4.0 We already posted a complete how to guide on how to Jailbreak iOS 4.0 / 4.0.1 iPhone 3GS with Jailbreakme. Following are the instructions to unlock iPhone 3GS with iOS 4.0 / 4.0.1 with Ultrasn0w.
Instructions to install ultrasn0w using cydia
Step One : Press to launch Cydia Installer from your Springboard.
Step Two : Press to select the Manage tab at the bottom of the screen.
Step Three : Press to select the large Sources button
Step Four : Press the Edit button at the top right of the screen.
Step Five : Press the Add button at the top left of the screen.
Step Six : Enter http://repo666.ultrasn0w.com as the source url and press the Add Source button.
Note:ultrasn0w is spelled with a zero, not the letter “o”.
Step Seven : Once the source has been added press the large Return to Cydia button.
Step Eight : Press the Done button at the top right of the screen.
Step Nine : Press to select http://repo666.ultrasn0w.com/ from the list of user entered sources.
Step Ten : Press to select ultrasn0w from the list of packages.
Step Eleven : Press the Install button at the top right of the screen.
Step Twelve : Press the Confirm button at the top right of the screen.
Step Thirteen : After installation completes successfully press the reboot.
Step Fourteen : Now press the Home button then power off and power on the iPhone. You do this by holding down the power button for 3 seconds then moving the power slider that appears to the right. Press the power button again to turn on the phone.
Step Fifteen : You should now be able to insert the SIM of your choice!
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