iPhone Dev Team’s ultrasn0w 1.2 works well to unlock iPhone 3GS & 3G 4.2.1 if they’re on baseband 06.15.00. You should jailbreak 4.2.1 & update 05.14.02 or 05.15.04 to 06.15.00 baseband in order to get iOS 4.2.1 unlock for 3G and 3GS iPhone versions. We’ve already posted a PwnageTool tutorial for those who want to use PwnageTool 4.1.3 (Mac only). Here is our guide for those Windows and Mac users who want to use redsn0w 0.9.6 Beta 5 to jailbreak and update iPhone 3G and 3GS baseband to 06.15.00:
Before you Begin:
Download iOS 4.2.1 firmware and update iPhone to iOS 4.2.1
Download Redsn0w 0.9.6 Beta 5 [Windows | Mac]
Step 1: Launch Redsn0w, click on “Browse” and select the downloaded iOS 4.2.1.
Step 2: 3GS users, Redsn0w will show a dialog box asking if you have new bootrom or old one. Click “Yes” if you have new bootrom iPhone 3GS and click “No” if you have old bootrom version.
Step 3: Redsn0w will show the following options:
- Install Cydia
- Install custom bundle
- Install iPad baseband
- Just boot tethered right now
- Just enter pwned DFU mode right now
Select “Install Cydia”, that’s obvious of all. Also select “Install iPad baseband” if (and only if) you want to unlock iPhone 3GS or 3G 4.2.1 iOS with ultrasn0w 1.2.
Be sure to read the warning that redsn0w shows when you check the “Install iPad baseband” checkbox.
Step 4: In next step, connect your device to computer while it’s turned off. Then click “Next”. Be ready to perform some quick actions to enter DFU mode.
Step 5: Enter DFU mode, follow on-screen instructions that redsn0w shows.
Soon as your device gets into DFU mode, redsn0w will begin the jailbreak process and will also update 05.15.04 to 06.15.00 baseband in the process.
iPhone 3GS, 3G Unlock iOS 4.2.1
After jailbreaking and updating the baseband, iPhone 3G and 3GS users can follow our guide on how to unlock iOS 4.2.1 with ultrasn0w 1.2.