[How-To] Downgrade Firmware 4.0 to 3.1.3/3.1.2 *Update*
Thursday, June 10, 2010
Update : New method added
2nd Method
Surely some iOs4.0 holder will miss the MobileSubstrate! For those wishing to return to version 3.1.3 or earlier, I suggest this guide:
Requirements:
- iTunes 9.1.1 installed on your computer;
- Firmware 3.1.2 or 3.1.3 -> DOWNLOAD : iPhone / iPod ;
- RecBoot -> DOWNLOAD WIN - MAC ;
1) After you download everything you need to have installed and connected the iPhone and iTunes 9.1.1 Open RecBoot;
2) click on 'Enter Recovery Mode "and your iPhone will be in recovery mode;
MAC: You should click the Finder icon in the Dock, click "Go to Folder ..." Now look for the file "Hosts" and you insert the string.
WINDOWS: Follow the path "C: \ Windows \ System32 \ drivers \ etc \" open file "Hosts" and change.
4) Open iTunes and you hold down Alt (Mac) / Shift (Windows) and clicking the Restore firmware downloaded.
5) iTunes will return the error "1015". Now reopen RecBoot and click "Exit Recovery Mode" to exit the recovery mode.
Now you have the fw 3.1.3 or 3.1.2 on your device. To jailbreak, you must use Spirit or Blackra1n respectively. 
1st Method
Here is a little tutorial to downgrade your Firmware 4.0 to 3.1.3.
- Check that you have the latest version of iTunes installed
- Connect your iPhone to your computer
- Set your iPhone in DFU mode (hold Home button for 5s, hold Power for 10s and finally release Power and keep holding Home button until iTunes detects your iPhone)
- Select Firmware 3.1.3 and restore your iPhone. Even if you have some issues message, ignore them, it doesn't matter
- Start Redsn0w and jailbreak your iPhone
