With recent iPhone firmware 4.2.1, it has become difficult to unlock and jailbreak iPhone. The latest version of redSnow doesn’t support all the basebands. As a result, users are still stuck on the older basebands.
Note: This guide is good for users who are still on 05.14, 05.15 or higher basebands and who want to upgrade their baseband. With this tutorial, your iPhone baseband will be updated to 06.15 baseband. Remember, after you upgrade your iPhone baseband to 06.15, you can’t restore it to factory defaults or to any other lower baseband. Also, if you don’t upgrade to a newer baseband, you can't enjoy the upcoming firmware updates.
This guide is for MAC users only.
If your iPhone has a lower baseband and is already unlocked, you can follow this guide to upgrade your iPhone to firmware 4.2.1 without upgrading the baseband.
2: If your iPhone has a lower baseband, you should read the other guide mentioned above. If your iPhone has firmware 4.2.1, you can move to the next step. Others continue reading…
Launch iTunes. Make sure your iPhone is connected to the computer. Once iTunes detects the iPhone, press the Shift key and click the Restore button. Choose the firmware file that you had just downloaded to restore your iPhone with firmware 4.2.1.
This process takes time, so please be patient. Your iPhone will boot several times during the process. Move to step 3, once your iPhone is restored to firmware 4.2.1.
3: Launch the RedSnow application and click the Browse button to select the iPhone 4.2.1 firmware file that you downloaded.
After the file has been verified by redSnow, you will be asked if your iPhone 3GS is new bootrom or old bootrom. If your iPhone 3GS is new bootrom, select ‘Yes’, otherwise, select ‘No’. Click the Next button to continue with the process.
4: RedSnow will now prepare the jailbreak process. From the list of options that appear, make sure you have selected the following: “Install Cydia and Install iPad Baseband”. Click the Next button when done. If after jailbreak, your Cydia icon is grey or the Cydia app doesn’t open; you should follow the process again and select the “Just boot tethered right now” option as well.
5: Now, you will be asked to put your iPhone in DFU mode. You can read the guide here: “How to put your iPhone in DFU mode?”
6: iPad baseband will be downloaded and your iPhone will reboot several times during the process. Since, iPad baseband is downloaded from the internet, please be patient. Click Finish when done.
Your iPhone is now jailbroken. To unlock your iPhone follow the guide here: Unlock your iPhone 3G, 3GS and iPhone 4 on 4.2.1 firmware.
RedSnow application screenshots by RedSnow