Now that Redsn0w 0.9.6rc9  finally provides the long awaitediOS 4.3.1 untethered jailbreak, many iPhone 4 owners with unlocked iPhones’ have been advised to hold off upgrading to 4.3.1 as you will lose the ability tounlock, since the newer firmware will update your baseband.

Furthermore, as we’ve mentionedearlier this morning, the new iOS 4.3.1 firmware currently is incompatible with the Dev Team’sultrasn0w unlocktool. It is recommended that you wait for the Dev Team to update this tool before upgrading and jailbreaking.

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But for those anxious to update to the new iOS 4.3.1 firmware and still preserve theiriPhone 4 1.59.00 basebandso they can be guaranteed an unlock when the Dev Team updates their ultrasn0w tool, follow our tutorial below.In thistutorial, we will show you how to upgrade your iPhone 4 to iOS 4.3.1, without upgrading its baseband, usingTinyUmbrella for Windows.

For those using a Mac, follow ourtutorial hereto preserve your baseband usingPwnage Tool.

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Windows users follow our guide below to update your iPhone 4 to iOS 4.3.1 and preserve your 1.59.00 baseband.

NOTE:This will only work for the iPhone 4.

If you are unsure as to what baseband your iPhone 4 is on, launch Settings > General > About  > Modem Firmware.

Step 3:Click On the “Save SHSH” button

Step 4:Now, Click on start the “TSS Server” button

Step 5:While the TSS server is running,Launch iTunes

Step 6:Now, Click onRestorein iTunes (Don’t Click on Update)

Step 7:During the Restore Process, iTunes will give youError 1013.Don’t panic, this is good. This error means your baseband has been preserved. Exit out of iTunes.

Step 8:Place your iPhone intoDFU modeby holding down both the Power and Home buttons for ten seconds, then release the Power button and continue holding the Home button for another 5 seconds.

Step 9:Fix Recovery in TinyUmbrella is currently not working. Download this standalone .exe file to fix recovery on 4.3.1. Extract the file and double click on fixrecovery43.exe. A command prompt will open, and the program will go through the process. During this time, you will notice scrolling text on your iPhone 4.

Step 10:Your iPhone will now be on 4.3.1 with the 1.59.00 baseband! Tojailbreakyour iPhone 4 on iOS 4.3.1, follow ourtutorial here!

Update: The iPhone Dev Team hasreleased an updated versionof the ultrasn0w unlock tool that is compatible with iOS 4.3.1.

Note:This will only unlock iPhone 4 on 1.59.00 baseband.Follow the tutorial hereto unlock your iPhone 4 on iOS 4.3.1.