The iOS 4.3.1 jailbreak has also been achieved, a few hours after the release of the iOS 4.3.1 firmware. If you are OK with a tethered jailbreak, then I could help you jailbreak iPhone 4 4.3.1 iOS using PwnageTool on Mac OS X. So, here are the instructions to jailbreak iPhone 4 4.3.1 iOS :

 

Jailbreak iPhone 4 4.3.1 iOS

Jailbreak iPhone 4 iOS 4.3.1

1. Download PwnageTool 4.2.

2. Download the PwnageTool bundle for iPhone 4 iOS 4.3.1 from here

3. Download iOS 4.3.1 IPSW from here

4. Move all the files to the desktop.

5. Right click the PwnageTool 4.2 icon and choose ” Show Package Contents “.

6. Browse to Contents/Resources/FirmwareBundles/ and paste the Old / New Bootrom bundle file here.

7. Download Ramdisk Fixer 1.7.1 from here and install it.

8. Now start PwnageTool and choose the expert mode.

9. Browse to the iOS 4.3.1 firmware IPSW.

10. Click on the build button after you chose the iOS 4.3.1 IPSW.

11. Launch iTunes and let it detect your iPhone.

12. Now restore your iPhone 4 to this newly created iOS 4.3.1 firmware. Go to iTunes and hold the alt key and click on ” Restore “. Now browse to the cooked firmware and select it. Wait till the iPhone reboots.

Tetheredboot Instructions

1. Download TetheredBoot from here and extract it.

2. Make a copy of the iPhone 4 iOS 4.3.1 custom firmware and change its extension to .zip.

3. Extract the custom iOS 4.3.1 zip file you just created.

4. Now copy the files under /Firmware/dfu/.

5. Move the kernelcache.release.n90 and iBSS.n90ap.RELEASE.dfu files to the tetheredboot utility folder.

6. Now, switch off your iPhone 4 and launch Terminal and enter the following commands :

sudo -s

cd /User/Desktop/Tetherboot/

./tetheredboot iBSS.n90ap.RELEASE.dfu kernelcache.release.n90

7. You will be asked to enter DFU mode. For that, hold the power and home button together for 10 seconds and then release the power button but keep holding the home button for another 10 seconds. Then release it.

That’s it! You have done it! After the reboot, you’ll find your iPhone 4 jailbroken on iOS 4.3.1.