How to: Downgrade iOS 4.1 to iOS 4.0

Yesterday we reported that iOS 4.1 has been released and many of the users have already updated their iPhone 3G/3GS, iPhone 4 and iPod Touch 2G/3G using iTunes restore. The jailbreak turnaround was really quick with this iOS update as the jailbreaking procedure remained unchanged for iPhone 3G and iPod Touch 2G on iOS 4.1 with redsn0w 0.9.5 Beta 5.

In case you didn’t find iOS 4.1 very impressive or are facing some issues on your device, you can opt to downgrade your device to iOS 4.0. Here are the step by step downgrading instructions from iOS 4.1 to iOS 4.0.

Please note that downgrading your iDevice using this method will change your baseband and you won’t be able to unlock it using the usual carrier unlock. Proceed with caution and at your own risk.

The first step is to download Original iOS 4 firmware and save it on your desktop [ Or wherever your prefer].
Now download iRecovery And LibUSB Library package according to your operating system. [All download links are provided at the end of the post].
Now connect your iPhone/ iPod Touch to the computer and restore to iOS 4.0 IPSW file through iTunes 9.2. You might encounter 1015 error while the restore process is taking place, don’t worry and click Ok to exit iTunes.
Now go to windows > Run > Type “CMD”. In the command prompt, type:

cd Desktop

. / iRecovery -s

setenv auto-boot true

saveenv

fsboot

exit

In case you are using Mac, type the same commands mentioned above in Terminal.
Now unplug your phone from the computer and reboot your phone by holding the home and power buttons together.
You phone might end up in recovery, you can exit the recovery mode by using iRecovery and LibUSB Library. [Step by step guide on using iRecovery to exit iPhone and iPod Touch recovery mode is posted here]

And there you go! If you have followed these instructions closesly, your iPhone 3G/3GS, iPhone 4 or iPod Touch 2G will be running stock iOS 4.0.

Reference Links:

Download iRecovery [(https://chronicdev.googlecode.com/files/iRecovery-Mac.zip) Mac, (https://www.zaksenterprises.com/Start-download/iPhone-Files/32-iRecovery-windows.html) Windows] and LibUSB [(https://www.ellert.se/PKGS/libusb-2009-09-10/10.6/libusb.pkg.tar.gz) Mac]

Download:

iOS 4 For iPhone 4

iOS 4 For iPhone 3GS

iOS 4 For iPhone 3G

iOS 4 For iPod touch 2G

iOS 4 For iPod touch 3G