How to Update to iOS 4.3.1 and Preserve iPhone 4 1.59.00 Baseband [Tutorial]

Now that Redsn0w 0.9.6rc9  finally provides the long awaited iOS 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 to unlock, since the newer firmware will update your baseband.

Furthermore, as we’ve mentioned earlier this morning, the new iOS 4.3.1 firmware currently is incompatible with the Dev Team’s ultrasn0w unlock tool. It is recommended that you wait for the Dev Team to update this tool before upgrading and jailbreaking.

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

For those using a Mac, follow our tutorial here to preserve your baseband using Pwnage Tool.

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 1: Download TinyUmbrella from here
Step 2: Connect your iPhone 4 & Launch TinyUmbrella

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 on Restore in iTunes (Don’t Click on Update)

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

Step 8: Place your iPhone into DFU mode by 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! To jailbreak your iPhone 4 on iOS 4.3.1, follow our tutorial here!


Update: The iPhone Dev Team has released an updated version of 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 here to unlock your iPhone 4 on iOS 4.3.1.