You can jailbreak iOS 4.0.2 on iPhone 3GS (Old bootrom) with the unofficial build of PwnageTool. For those who don't know, Apple released iOS 4.0.2 for iPhone 4, 3GS, 3G and iPod Touch 2G, 3G fixing the PDF exploit which enabled all iPhone, iPod Touch and iPad users to jailbreak their devices on all firmwares. If you are on iOS 4.0 / 4.0.1 or less, you can use this PDF patch to save your device from PDF vulnerability without updating firmware to iOS 4.0.2.
If you have upgraded your device firmware to iOS 4.0.2, you can still downgrade from iOS 4.0.2 to iOS 4.0 / 4.0.1 / iPhone OS 3.1.x by using the step-by-step guide here. However if you want to jailbreak iOS 4.0.2 on iPhone 3GS (Old bootrom), follow the steps-by-step guide below:
Jailbreak iPhone 3GS on iOS 4.0.2 with PwnageTool (Unofficial)
*Find all download links at the bottom of the post.
- *Download latest version of iTunes.
- *Download iOS 4.0.2 for iPhone 3GS
- *Download PwnageTool 4.0.2
- Connect your iPhone to iTunes and sync to backup all of your data including apps, contacts, messages and photos etc
- Place PwnageTool, iOS 4.0.2 IPSW and kernelcache.release.n88 on your desktop.
- Launch PwnageTool and click OK to accept the warning message.
- Click on iPhone 3GS and hit the next button at the bottom-right of the window.
- Now PwnageTool will automatically detect iOS 4.0.2 IPSW file from your desktop and validate it. Incase PwnageTool fails to detect the iOS 4.0.2 IPSW, click on the Expert Mode button at the top, browse for iOS 4.0.2 IPSW manually and click next button.
- Now PwnageTool will ask Do you have an iPhone contract that would activate normally through iTunes?, choose NO if you are on unofficial carrier and YES if you are on official carrier like AT&T. Remember clicking YES will upgrade your baseband to the latest version.
- Now PwnageTool will show the final popup after which it will start creating a custom cooked IPSW file on your desktop. Click Yes button to continue.
- Wait for 4-5 mins while PwnageTool creates a custom IPSW file of iOS 4.0.2 which will be placed on your desktop.
- During the creation of custom IPSW by PwnageTool, you will be prompted to enter the Administrator password. Enter your correct Administrator username and password.
- Once you see "ihaz Success" on your screen, you are all done!
- Check your desktop, you will see custom IPSW file of iOS 4.0.2 cooked by PwnageTool for your iPhone.









How to Restore Custom IPSW File of iOS 4.0.2 with iTunes
Once you have got the custom IPSW file of iOS 4.0.2, connect your iPhone to your computer and start iTunes. Click on the name of the iPhone on the sidebar of iTunes to go to the summary panel. You will see two buttons i-e "Check for Update" and "Restore". Hold down the SHIFT key (ALT key for Mac) and click on the "Restore" button, browse to the IPSW file of iOS 4.0.2 which you just cooked with PwnageTool. Sit back and relax while iTunes restore jailbroken iOS 4.0.2 on your device.
Unlock iPhone 3GS on iOS 4.0.2 with Ultrasn0w 1.1-1
Once you have jailbreaked iOS 4.0.2 on iPhone 3GS (Old bootrom), you can now unlock your device by using Ultrasn0w 1.1-1.
Download Links:
Download iTunes 9.2.1
Download PwnageTool 4.0.2 | Mirror
Download iOS 4.0.2 for iPhone 4, 3GS, 3G & iPod Touch 2G, 3G
Update1: Jailbreak iOS 4.0.2 on iPhone 3G & iPod Touch 2G with Redsn0w 0.9.5b5-5
Update2: Sn0wbreeze 2.0 Jailbreaks iPhone 3GS (Old Bootrom) on iOS 4.0.2
Thanks to Stefano for the tip via email!

(Thanks to Stefano for the tip)
Update: After creating the custom IPSW through PwnageTool, rename it from .IPSW to .ZIP and open it with WinZip or WinRAR, replace kernelcache.release.n88 and then rename it back from .ZIP to .IPSW.




