How To Unlock iOS 4.2.1 on iPhone 3G and 3GS with RedSn0w 0.9.5b5 and UltraSn0w 1.2

Simple instruction on how to unlock your iPhone 3G and 3GS running on iOS 4.2.1 with RedSnow [RedSn0w] and UltraSnow [UltraSn0w] 1.2.

Jailbreaking and unlocking your iOS 4.2.1 is very simple. But before proceeding, you have to be sure that you know what you are doing or you know someone who does in case something goes wrong.

To unlock your iPhone 3G or 3GS, you need to update your iPhone modem baseband to an unsupported Apple baseband version [Baseband 16.15.00]. Baseband 16.15.00 which is an iPad baseband.

The following procedure will guide you on how to jailbreak and unlock your iPhone 3G or 3GS with iOS 4.2.1.

WARNING!

You do this procedure at your own risk. Please understand the consequences of updating to baseband 16.15.00.

1. There is no way to come back down from 06.15, and there’s no hiding the baseband version from Apple. You’ll be voiding your warranty in a very obvious way.
2. If some future baseband comes out with a critical fix, you won’t be able to update to it if it remains down in the 05.xx sequence (then again, you wouldn’t update to it if you wanted to keep your unlock anyway).
3. Starting with FW 4.2.1 if you have 06.15 on your iPhone you won’t ever be able to restore to stock firmware (it will fail). You’ll need to only restore to custom IPSWs (then again, if you’re an unlocker you should already be doing that).

The new redsn0w 0.9.6b5 fetches the 06.15.00 baseband files directly from Apple for now (the only IPSW you ever point it at is the stock IPSW for the FW on your iPhone right now). There may be a long delay while it’s doing this (their servers are currently getting pounded).

Supported devices:

This version of redsn0w 0.9.6b5 is developed ONLY for iPhone 3GS and 3G users who rely on unlock. Precisely, This guide showing how to jailbreak and update baseband to 06.15.00 for ONLY iPhone 3GS and 3G who have unlocked devices. Ultrasn0w unlock is not yet supported for iPhone 4.

Unsupported devices:

iPhone 4 and 3GS users who don’t rely on unlock should follow the same guide but with redsn0w 0.9.6b4 to jailbreak their devices on iOS 4.2.1.

What you need:

RedSn0w 0.9.6b5 | download [Windows] [Mac]

iPhone 3G and 3GS running on iOS 4.2.1 | (If you don’t have iOS 4.2.1 in your iPhone, you can update it via iTunes.)

iOS 4.2.1 latest firmware | Download [3G] [3GS]

Latest iTunes version | download [Here]

Procedure:

1. Launch Redsn0w 0.9.6b5, and browse for iOS 4.2.1 firmware final version.

2. Click NEXT.

3. Tick “Install Cyndia” and “Install iPad Baseband”, and then click NEXT.

Warning: If you proceed with the iPad baseband install, you won’t be able to go back to your previous baseband. Be sure that you know what you are doing, or you have someone nearby who does in case something goes wrong with the jailbreak and the install.

4. Now make sure your device is both OFF and PLUGGED IN to the computer before you click NEXT.

5. At this stage you will need to put your iPhone in DFU mode by holding “Power” button and then while holding the “Power” button, you will now have to hold “Home” button too. Now after few seconds release “Power” button but keep holding “Home” button until installation begins.

6. After the redan0w is done working its magic you will get a jailbroken iPhone on the latest iOS 4.2.1 and the unlockable baseband 06.15.00.

Once you jailbreak your device, you can now unlock your iPhone on baseband 06.15.00 using Ultrasn0w 1.2 from Cydia.

Enjoy!