How to Downgrade iPhone 3GS to iOS 4.1 for Untethered Jailbreak and Unlock Baseband 6.15.00
Did you accidentally try to update your iPhone 3GS with baseband 6.15.00 to iOS 4.3.5 and then now you’re stuck on recovery? You know there’s no untethered jailbreak unavailable for iOS 4.3.5 and Apple doesn’t allow you to downgrade to earlier iOS versions unless you have your SHSH blobs saved.
UPDATE: Forget about installing iPad baseband or hacking your iPhone, make it officially unlocked here.
Thankfully, there’s still a resolution for this issue. Oddly, Apple is silently signing iOS 4.1 for 3GS which means you can downgrade to this version and have an untethered jailbreak.
Here are the steps:
1. Download iOS 4.1 firmware for iPhone 3GS from here.
2. Download sn0wbreeze 2.1 from here.
3. Launch sn0wbreeze and build a custom firmware (for beginners choose simple mode). You can also download iOS 4.1 hacktivated custom firmware from here. Once done, iREB will guide you on how to pawn-DFU your iPhone to allow it to accept custom firmware. Simply follow the on-screen instructions.
Note: You can also use redsn0w 0.9.6rc17 to pawn DFU your iPhone.
4. Check to make sure your host file will only point to Apple server. If you’ve used TinyUmbrella before, there’s a chance that the host file is set to Saurik’s server. A clean host file will look something like this:
5. To edit your host file, go to C:\WINDOWS\system32\drivers\etc. Right click ‘hosts’ file and open it with Notepad (on Windows 7 or Vista, right click and choose Run as Administrator). Remove any line that shows gs.apple.com
6. Launch iTunes, click Shift+Restore and point to the custom firmware.
7. Sit back and relax while iTunes begin restoring your iPhone.
8. Your iPhone is already in jailbroken state (Cydia installed) once restore is complete. You can now unlock it with ultrasn0w.
Any issues? Leave your comments below.
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