The dev-team has released redsn0w version 0.9.6b5 for iOS 4.2.1 which will help update the baseband 5.14.02 and 5.14.04 to baseband 06.15.00 and carrier unlock it with the newly released ultrasn0w 1.2
- There is no way to come back down from 06.15, and there’s no hiding the baseband version from Apple. You’ll be voiding your warranty in a very obvious way.
- If some future baseband comes out with a critical fix, you won’t be able to update to it if it remains down in the 05.xx sequence (then again, you wouldn’t update to it if you wanted to keep your unlock anyway).
- Starting with FW 4.2.1 if you have 06.15 on your iPhone you won’t ever be able to restore to stock firmware (it will fail). You’ll need to only restore to custom IPSWs (then again, if you’re unlocker you should already be doing that).
Certainly don’t update to 06.15 if you don’t need to! Only do this if you need the unlock and you’re stuck on 05.14 or 05.15, and you’re willing to assume the above risks.
Let's get on with how to do it:-
1) Make sure you have iTunes 10.1 before you start with the jailbreaking. You can download iTunes 10.1 here or you can update your iTunes via the apple software update.
2) Download the iOS 4.2.1 ipsw file:
3) Download redsn0w 0.9.6beta5 from here
4) Run redsn0w.exe
Please note: If you're using windows 7, you will have to use redsn0w in "XP Compatibility" mode.
5) Click on browse and select the iOS 4.2.1 ipsw file.
6) If you have an iPhone 3GS, it will ask you if you have the NEWER fixed bootrom version of the iPhone 3GS. To check if you have a "newer" version go to your settings > about on your iPhone 3gs and check the serial number. The 4th and 5th digit is the week number you're looking for. If the number is >45 you have a newer device and need to click yes, otherwise it's an old device and you need to click no when it asks if you have a newer device. For example if the 4th digit is 4 and the 5th digit is 8, that's week 48 and a newer device. Then click "next"
7) Allow the kernel to be patched.
8 ) On the next screen click on "Install cydia" and "Install iPad baseband" and click Next.
9) Make sure your device is powered off and plugged in and click next.
10) Put your iPhone 3g/3gs in DFU mode:
A. Hold down the Power/Sleep button for 3 seconds.
B. Without releasing the Power button, also hold the Home button for 10 seconds.
C. Without releasing the Home button, release the Power button but Keep holding the home button for another 15 seconds.
11) Wait for redsn0w to get the iPad baseband file (This may take long because of apple's servers being very busy)
12) That's it. The remaining process takes place on the iPhone itself.
13) That's it. Your baseband is now updated to 06.15.00. Next thing you need to do, is the carrier unlock
14) Go to cydia > manage > sources > edit > add and and type "http://repo666.ultrasn0w.com/" without the quotes and click on "add source"
15) Once the source is added, press return to cydia and done.
16) Now select repo666.ultrasn0w.com from the list of sources and click on ultrasn0w.
17) Once it installs, reboot your device.
18) That's it. Once the phone starts, you will have an unlocked jailbroken iPhone on 4.2.1
Hope this guide was useful.