The following step by step guide will help you downgrade your iPhone with firmware 3.1 to firmware 3.0.1. For those of you who upgraded to iPhone 3.1 may have found your device to be locked and un-jailbreakable as the tools for jailbreaking and unlocking are not out yet for iPhone OS 3.1. Fortunately, there is still a way to downgrade your phone from firmware 3.1 to 3.0.1. I have tried it on my iPhone 3G and it works perfectly on it. It should also work on the original iPhone (aka iPhone 2G). This method wont work on iPhone 3GS. Also to note here is that while this method will help you downgrade your firmware from 3.1 to 3.0.1, your baseband will not be downgraded which means you cant unlock it for now.
Step 1: Download and install iTunes 9 if you haven’t already.
Step 2: Download iPhone OS 3.0.1 firmware for your iPhone (3GS, 3G and 2G). Download links are given below.
Step 3: Now copy and paste the downloaded .ipsw file in the following location:
Mac OS X: "~/Library/iTunes/iPhone Software Updates" Windows 7: "\Users\[username]\AppData\Roaming\Apple Computer\iTunes\iPhone Software Updates" Windows Vista: "\Users\[username]\AppData\Roaming\Apple Computer\iTunes\iPhone Software Updates" Windows XP: "\Documents and Settings\[username]\Application Data\Apple Computer\iTunes\iPhone Software Updates"
Step 4: Connect your iPhone with your computer and start iTunes, press and hold shift key and then click on “Restore”.
Select the firmware 3.0.1 .ipsw file you downloaded in Step 2 and restore it. During the restore process, iTunes will throw you 1015 error which will say:
The iPhone “your iPhone” could not be restored. An unknown error occurred. (1015)
Just ignore this error and close iTunes.
Your phone will now be in recovery mode, showing iTunes logo and usb connector.
Step 5: Start QuickPwn 2.2-1 (download link given below) and perform the procedure prompted to you by QuickPwn to reset your device:
Once your iPhone has restarted, close QuickPwn.
Step 6: Start iTunes again with the original AT&T SIM card. iTunes should now show the firmware version as either 3.0 or 3.0.1 depending on which ever firmware you chosed to downgrade to in Step 2.
Step 7: You can now jailbreak your iPhone which you have downgraded from firmware 3.1 to 3.0.1 by following the step-by-step jailbreaking guide posted here.
Feel free to ask me any question regarding any problem that you may encounter during the downgrading process.
UPDATE 1: Downgrade of iPhone 3GS from firmware 3.1 to 3.0 is now possible. Follow the step-by-step guide posted here to downgrade iPhone 3GS with firmware 3.1 to firmware 3.0.
UPDATE 2: Jailbreak and unlock is now possible for iPhone 2G and iPhone 3G running firmware 3.1. Follow the complete step-by-step guide posted here in order to jailbreak and unlock your iPhone with firmware 3.1.
UPDATE 3: Downgrading of Baseband for iPhone 3G running firmware 3.1 is now possible. Complete step-by-step guide on how to downgrade your baseband from 05.11.07 to 04.26.08 can be found here.