As I promised yesterday that I will post about Downgrade iOS 4.0 To iPhone OS 3.1.3 For Mac, some people think that iOS 4.0 not too feature-rich or user friendly, thus for those who seek the tutorial to downgrade their OS to 3.1.3, here it is! Remember, if you use iPhone 3GS or iPod Touch 3G you need to firstly save SHSH blobs at Saurik or else you will experience trouble!
Download the following before continue:
- Download iTunes 9.2
- Download iPhone OS 3.1.3 firmware for iPhone 3G and 3GS
Change your communication server from Apple to SaurikFor Mac Users:
- Hit Go then go to folder and then enter the path /etc. Now open the file : HOSTS using TextEdit and paste the line (below) right at the end of the entire file in TextEdit (see the screenshot for example)
74.208.10.249 gs.apple.com

- If there is no extension provided just uncheck, so just use extension .txt box – then save it and then name the file hosts without extension, now put it on your desktop!
- Now drag the file you just saved and drop it to /etc! With this you are changing your communication server from Apple to Saurik, since your ECID is on that server! Then put your iPhone in DFU mode to restore any previous OS (If you are asking for password during the changing just enter and click ok)
Steps To Downgrade iOS 4.0 To Firmware 3.1.3 on Mac
- Download and extract iRecovery v1.3.zip and put it on your desktop
- Now you need LibUSB library, download it and install it.
- Head to iTunes then hit ALT+Restore to load your the iPhone 3.1.3 firmware manually.
- You will likely see error code 1015 appear in a popup, if that’s so, ignore it! Just close it by clicking ok and close iTunes too
- Open terminal and type the following command at the terminal:
cd Desktop. /-s iRecovery setenv auto-boot true saveenv fsboot exit
- Now it’s time to disconnect your iPhone from the cable, but wait for a few seconds before you disconnect it
- Now hit HOME and POWER buttons at the same time to restart your PHONE
- When Apple logo appears on your screen, connect the phone to Mac via cable and proceed normally with the activation process.
- Now your OS is downgraded from iOS 4.0 To Firmware 3.1.3 on Mac!
For Windows Downgrade iOS 4.0 To iPhone OS 3.1.3 For Windows