The official PwnageTool bundle to upgrade iOS 4.2.1 on iPhone 3GS (Old bootrom) while preserving its unlockable baseband has been released by iPhone Dev-Team. Follow this guide if you rely on an unlock and want to upgrade your iPhone firmware to iOS 4.2.1 without loosing your unlock.
Note: The following guide will NOT (actually) jailbreak your iPhone 3GS (Old bootrom) but will help you to upgrade your iPhone firmware to iOS 4.2.1 without upgrading its current unlockable baseband. After following the guide below, you still need to use Redsn0w 0.9.6b5 to actually jailbreak your iPhone on iOS 4.2.1. As it is iPhone 3GS with old bootrom, so the jailbreak will be untethered.
Steps to Upgrade iOS 4.2.1 on iPhone 3GS (Old Bootrom) with PwnageTool:
- Download and install iTunes 10.1 from here
- Download PwnageTool 4.1.3 from here
- Download iOS 4.2.1 firmware for iPhone 3GS from here
- Download iOS 4.2.1 PwnageTool bundle for iPhone3GS from here
- Create an empty directory on your desktop and rename it PwnageTool 4.1.3
- Place PwnageTool, iOS 4.2.1 IPSW for iPhone 3GS (iPhone2,1_4.2.1_8C148a_Restore) and PwnageTool bundle file (iPhone2,1_4.2.1_8C148a.bundle) in the directory you created in step 5.
- Right-click on PwnageTool app, choose Show Package Contents and navigate to Contents/Resources/FirmwareBundles/
- Copy or drag iOS 4.2.1 bundle file (iPhone2,1_4.2.1_8C148a.bundle) in FirmwareBundles directory as shown in the screenshot below:
- Launch PwnageTool, click on the Expert mode, select iPhone 3GS, 3G, 4 from the displayed options and click Next button to continue.
- Click on the browse and select iOS 4.2.1 IPSW for iPhone 3GS (iPhone2,1_4.2.1_8C148a_Restore) that you downloaded in step 3
- Select General tab and click on the Next button.
- Uncheck Activate the phone from the given options and click Next button.
- Click on the Build tab and click on the Next button to continue.
- Now PwnageTool will prompt you to select the directory where you want to save iOS 4.2.1 custom IPSW file for iPhone 3GS. Select Desktop from the drop-down list and click Save button.
- Now wait while PwnageTool build iOS 4.2.1 custom IPSW for your iPhone 3GS.
- Once done, connect your iPhone to your Mac through USB cable and hold down the Power and Home button simultaneously for 10 seconds, after 10 seconds release the Power button but continue holding the Home button until PwnageTool detects your iPhone in DFU mode.
- Thats it! Now you can find iOS 4.2.1 custom IPSW (iPhone2,1_4.2.1_8C148a_Custom_Restore.ipsw) on your desktop.
Steps to Restore iOS 4.2.1 Custom IPSW Through iTunes:
Once you have successfully created the iOS 4.2.1 custom IPSW through PwnageTool and your iPhone is in DFU mode, launch iTunes and click on the name of the device from the side panel to view the summary page.
Now you will see two buttons, Check for Updates and Restore. Hold down the ALT key (SHIFT for Windows) and click on the Restore button to browse for iOS 4.2.1 custom IPSW file you just created with the patched version of PwnageTool 4.1.3
Above image is for illustration purpose only
Now wait until iTunes restores the custom cooked iOS 4.2.1 IPSW on your iPhone 3GS. If you see iTunes error 1004 or 1015 during the restore, don't panic because the firmware restore on your device is now complete. All you need is to kick your device out of recovery mode by using RecBoot or TinyUmbrella software.
Now that you have restored iOS 4.2.1 on your iPhone 3GS without upgrading its baseband, you must follow step-by-step guide here (Skip step 4 & uncheck "Install iPad baseband" option in 8th step) to jailbreak your device with Redsn0w 0.9.6b5. Once done, use this guide to unlock your iPhone 3GS (Old bootrom) with Ultrasn0w 1.2. [via DEV-TEAM BLOG]
Update#1: Fix iPhone 3G/3GS Battery Drainage & Overheating Problems on iOS 4.1/4.2.1
Update#2: How to Activate iPhone 4/3GS/3G without Official SIM with SAM
Update#3: Download official PwnageTool 4.2 for untethered iOS 4.2.1 jailbreak on Mac
Update#4: Download Sn0wbreeze 2.2 for untethered iOS 4.2.1 jailbreak on Windows