I have talked to a few members on our site who have already updated to 4.3.1 because they did not know that updating could ruin their chances to jailbreak. We must stress that you should NEVER update your firmware unless you know for a fact that the firmware you are updating to is jailbrekable, or at the very least, make sure you have your SHSH saved for an earlier firmware so you can downgrade if need be. However, for those of you who are now stuck on 4.3.1 thankfully you can now perform a tethered jailbreak using Pwnage Tool 4.2 and 4.3.1 firmware bundle.

Downloads:
Pwnage Tool 4.2 (Mac)
4.3.1 Firmware Bundle
Tethered Boot Files
RamdiskFixer 1.5
Factory 4.3.1 firmware for your device

Step 1: Extract the custom bundle and copy the "iPhone3,1_4.3.1_8G4.bundle" file.

Step 2: Place the Pwanage Tool 4.2 downloaded earlier in "Application" folder and right click and select “Show Package Contents”.

Step 3: Browse to "browse to Contents/Resources/FirmwareBundles/" and paste the " iPhone3,1_4.3.1_8G4.bundle " file from Step 1.

Step 4: Now install the RamDisk Fixer pakage to enable the iOS 4.3.1 support on Pwanage Tool 4.2.

Step 5: Now run Pwanage Tool and select Expert Mode and mark iPhone.

Step 6: Now locate the iOS firmware 4.3.1 where it resides.

Step 7: After loading firmware, Choose"create custom iOS 4.3.1 GM IPSW."

Step 8: After creating the ISPW, get iPhone in DFU mode by clicking onDFU icon and following the instructions.

Step 9: Launch iTunes select iPhone as device then click on "Restore" Button while pressing the "Alt" key on keyboard.

Step 10: Wait For installation to finish.

Step 11: Now you are jailbroken on 4.3.1

But wait, remember that this jailbreak is tethered. So every time you reboot you have to be connected to a computer and manually boot up the phone by following these directions:

1. Change the extension of custom iOS 4.3.1 form ipsw to zip.
2. Now extract this custom firmware and copy “kernelcache.release.n90” and“iBSS.n90ap.RELEASE.dfu” files from” /Firmware/dfu/” and paste into tetheredboot folder after extracting the tetheredboot.zip.
3. Turn your device OFF and run the terminal. Type following commands   “sudo -s”
4. Enter the Admin Password, now run the following commands :-

• /Users/engineerhead/Downloads/tetheredboot/tetheredboot
• /Users/engineerhead/Downloads/tetheredboot/iBSS.n90ap.RELEASE.dfu
• /Users/engineerhead/Downloads/tetheredboot/kernelcache.release.n90

Make sure that tetheredboot folder is in Downloads Folder and replace “engineerhead” with your user name.

At some stage, you will need to get you’re device into DFU.

• Press Home and Power button together for 10 seconds.
• After 10 seconds release the Power button but continue holding home for another 10 seconds.
• If you are having troubles getting into DFU mode, check out our DFU mode video tutorial

Some processing will be done on iPhone and your iPhone will now again be in a jailbroken state running iOS 4.3.1