How to Jailbreak and Unlock iPhone 3GS 4.2.1 Firmware

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Although, DEV Team has released a jailbreak and unlock process for iPhone 3G, iPhone 3GS (old bootrom), iPhone 3GS (new bootrom) and iPhone 4 with 4.2.1 firmware, not all basebands are supported and iPhone users are finding it difficult to jailbreak and unlock their iPhones with different baseband versions. At present, redSnow for Windows only supports the following basebands: 01.59, 05.11.07, 04.26.08, 05.13.04, 05.12.01 and 06.15.

There has been a mixed response from people jailbreaking and unlocking iPhones, whereby, some users could not even jailbreak their iPhone, while others were able to jailbreak and unlock their iPhone, but were unable to get any network signals.

In this article, I will guide you on how to jailbreak and unlock your iPhone 3GS (old bootrom) on 4.2.1 firmware with a custom firmware file.

Note: This tutorial applies only to iPhone 3GS (old bootrom) with 4.2.1 firmware and 5.15.04 or 06.15 baseband. Before following the steps, make sure your iPhone is fully charged.

Step by Step Instructions

Step 1: If you have jailbroken your iPhone with 4.2.1 firmware following this tutorial,

"How to Jailbreak and Unlock 4.2.1 Firmware on iPhone 3G, 3GS and iPhone"

and have moved up from 5.15.04 to 06.15 baseband, then there is nothing to worry. Others, who are still on 5.15.04 baseband can also follow the steps listed here.

As a first step, download the custom firmware file from this link: iPhone 3Gs (old bootrom) Custom Firmware

Step 2: After you have downloaded the file, make sure the file extension is “ipsw”. Put your iPhone in DFU mode, following this tutorial: "How to Put iPhone in DFU mode"

Step 3: After you have put your iPhone in DFU mode, start iTunes. iTunes will detect your iPhone in recovery mode. Holding the Shift key, press the Restore button and select the custom firmware file that you have downloaded.

iTunes will now start the restore process. During the restore process, your iPhone may restart several times. Don’t interrupt the process; otherwise, you will end up with a bricked iPhone.

Step 4: Once iTunes has completed the restore process, follow this tutorial to jailbreak your iPhone using redSnow. DO NOT check the option to “Install iPad Baseband”, if your iPhone has now moved to 06.15 baseband. The rest of the process is the same.

Make sure to select the “Install Cydia’ option.

Step 5: After redSnow has finished jailbreaking your iPhone, you can now follow the unlocking guide here:

Unlock your iPhone 3GS (old bootrom) on 4.2.1 firmware using UltraSnow

You can now use your iPhone with any network service provider of your choice.

iPhone Jailbreaking Problems

You can also read about common iPhone jailbreaking problems encountered during the iPhone jailbreak and unlock process and find the answers to such problems. Read the article here:

Common iPhone Jailbreaking Problems and their Solutions