Restoring stock iOS 4.3 IPSW to your iPhone 3GS upgrades its baseband to 05.16.01. To unlock iPhone 3GS baseband 05.16.01 with Ultrasn0w, you must upgrade it to iPad baseband 06.15.00. It is the same iPad baseband hack which can be used to unlock iPhone 3GS/3G 05.15.04 & 05.14.02 baseband.
IMPORTANT UPDATE: DO NOT use this guide as it is outdated. Use this guide to fully jailbreak and unlock iPhone 3GS baseband 05.16.01 on iOS 4.3.3.
UPDATE#1: DO NOT use this method as iH8sn0w has released Sn0wbreeze 2.4b1 which helps you to upgrade to iPad baseband while jailbreaking iPhone 3GS on iOS 4.3.1. Just follow this guide to upgrade 05.16.xx to iPad baseband using Sn0wbreeze 2.4b1 and this guide to unlock it with Ultrasn0w.
UPDATE#2: iH8sn0w has just released Sn0wbreeze 2.5.1 which allows you to upgrade to iPad baseband without any 1002 or other restore error. Just download Sn0wbreeze 2.5.1 from here and follow this guide to upgrade to iPad baseband (Even if you are on iOS 4.3.1).
UPDATE#3: Downgrade iPad baseband 06.15.00 to 05.13.04 is very much possible!
UPDATE#4: Fix iPhone 3GS (iPad Baseband) Battery Life Issues on iOS 4.3.3 [Tips]
- After upgrading your baseband to 06.15.00, you can never downgrade your baseband back to 05.16.01. Until now, there is no tool available which can actually downgrade iPad baseband 06.15.00 to 05.16.01, 05.15.04 or 05.14.02.
- All those apps which use GPS will not work as GPS functionality is broken on iPad baseband.
- You can never restore stock IPSW of any firmware again on your iPhone. To downgrade or upgrade your firmware, you must use custom IPSWs made with PwnageTool or Sn0wbreeze.
Steps to Upgrade iPhone 3GS Baseband 05.16.01 to 06.15.00:
- Download and install iTunes 10.2.1 for Windows or Mac OS X from from here
- Download stock iOS 4.1 or iOS 4.2.1 for iPhone 3GS.
- Download Redsn0w 0.9.6b5 for Windows or Mac OS X
Make sure your iPhone is running stock iOS 4.3 IPSW. You can download stock iOS 4.3 IPSW for iPhone 3GS from here and restore it with iTunes 10.2.1.
- Launch Redsn0w 0.9.6b5 and click on the Browse button. Now you can either choose iOS 4.1 IPSW or iOS 4.2.1 IPSW for iPhone 3GS.
- Wait while Redsn0w processes the firmware file.
- Choose YES if you have iPhone 3GS with newer bootrom, otherwise choose NO. You can check the bootrom of your iPhone 3GS through iDetector software which you can download from here.
- Once IPSW has been successfully identified by Redsn0w, click on the Next > button.
- Wait while Redsn0w patches the kernel in IPSW.
- Choose "Install iPad Baseband" option from the list and click on the Next > button.
- Connect your iPhone to your PC or Mac via USB cable and make sure it is completely powered OFF.
- Now use the following instructions to put your iPhone in DFU mode:
- Hold down the Power (corner) button for 3 seconds.
- Without releasing the Power button, also hold down the Home (bottom center) button for 10 seconds.
- Without releasing the Home button, release the Power button BUT KEEP holding the Home button for 15 seconds until Redsn0w detects your iDevice in DFU mode.
- Now Redsn0w will fetch iPad baseband files from the server. This process usually takes a while, so please be patient.
- Once done, your iPhone will restart automatically. Click on Finish button to close Redsn0w.
- Thats it. Now your iPhone 3GS should be running iPad baseband 06.15.00.
Note#1: As confirmed by Mr. Jhey and Mr. Marcel, Redsn0w will not upgrade your baseband if you are running stock iOS 4.3 or custom iOS 4.3 on your iPhone 3GS. In order to use Redsn0w to upgrade to iPad baseband, you must first downgrade back to iOS 4.2.1 (Stock or custom IPSW) using this guide. Once downgraded to iOS 4.2.1, use Redsn0w to upgrade to iPad baseband and then restore custom IPSW of iOS 4.3 made with Sn0wbreeze 2.3b4.
Now download Sn0wbreeze 2.3b4 from here and use this guide to create iOS 4.3 custom IPSW for your iPhone 3GS. After creating custom IPSW, restore it with iTunes. After custom IPSW restore, use TinyUmbrella (FixRecovery) to kick your iPhone out of iOS 4.3 recovery mode loop. If you are iPhone 3GS (New Bootrom) user, you must use iBooty to boot your iPhone into a tethered jailbroken state. Last but not the least, use Ultrasn0w 1.2 to unlock your iPhone 3GS on iOS 4.3.