As we get closer to the end user release of the iOS 4 and the iPhone 4, many may be debating about updating their current iPhone 3GS — particularly if jailbreaking is on their minds. If you’re waiting to see how the new software will work in your hands, as well as jailbreaking for all those extra tweaks, a solution has been provided from the iPhone Dev team.
There are some prerequisites: You must ensure that your baseband is 04.26.08. (If your baseband is 05.11.07, you can use blacksnow RC2 and downgrade your baseband. If it’s 05.12.01, however, you’ve got to wait for the end of June to unlock your device.)
If you don’t know which Baseband is being used on your device then you can check by going to Settings > General > About > Version, it will be at the bottom labeled “Modem Firmware”.
Here’s how to unlock iOS 4 on your 3GS:
You will need to add a source into Cydia and step-by-step directions for that can be found by clicking on this link.
Once you have jailbroken your iPhone 3GS, you can now unlock running the custom iOS 4.0 firmware. You will need to use ultrasn0w 0.92.1 from Cydia.
Type “http://ios4.ultrasn0w.org/” letter for letter (without the quotes).
After the source has successfully been added to Cydia, you will need to search for “ultrasn0w 0.92” and install this application. Ultrasnow 0.92 will automatically unlock your iPhone 3GS enabling you to use your iPhone 3GS with any carrier.
Be sure to restart your iPhone after your installation is complete! Those who have worked with Cydia will know that this is necessary to fully install the new software installed on your iPhone.
If you would like a complete step-by-step guide for this unlock, click here for the tutorial, courtesy of Redmond Pie. If you need to use blacksnow RC2 to downgrade your baseband, you can watch it here:
Be sure to take heed with the warning provided as it is buggy and you may experience difficulties with downgrading your baseband.