We have already published guides on how to jailbreak iOS 4.1 on iPhone 3G & iPod Touch 2G (non-mc model). Now that you have already upgraded to iOS 4.1 only to find out Apple’s claim on fixing antenna issue is fake or aren’t impressed with iOS 4.1 beta then here is our working guide to downgrade iOS 4.1 to 4.0 on iPhone 3G, 3GS & iPhone 4.
But keep in mind that by downgrading iOS 4.1 to 4.0 your baseband won’t change and your iPhone will be locked if you are not on supported carrier. Hence unlockers must stay away from iOS 4.1 until iPhone dev team comes up with iOS 4.1 unlock tools.
Stuff you will need
1. iTunes 9.2 (latest iTunes)
Downgrade iOS 4.1 OS to 4.0 on iPhone 4, 3G & 3GS
1. Download iOS 4.0 firmware file.
2. Connect iPhone to computer
3. Now Start iTunes 9.2 and Windows (Alt Key+ Click Restore) Mac (Hold Option + Click Restore), Now manually select iOS 4.0 firmware.
4. During the restore process you will get an 1015 error. Don’t worry, that’s normal. Just click on Ok and close iTunes.
5. Now open terminal on Mac/ Command Prompt on Windows and type following commands
. / iRecovery -s
setenv auto-boot true
6. Now unplug your iPhone and turn it off by pressing the home+power button.
7. Once it is off, turn it on by pressing the power button. Plug-in your iPhone and load iTunes to continue with the activation.
That’s it we have successfully downgraded iOS 4.1 to 4.0 on iPhone. iPhone 3GS users can only downgrade to firmware 4.0, unless you saved your ECID files to a earlier version.
Please Note: Do it at your own risk, we will not be responsible for any damage that may arise to your iPhone by following above guide.