Apple has just released the iOS 4.1 beta update for iPhone and iPod Touch users. The new iOS4.1 update aims at fixing the signal woes the iPhone 4 has been facing. In addition to this, the iOS 4.1 update also changes the wrong signal calculation algorithm being used in iOS 4 and adds in new Gaming modules.
However, the problem with iOS 4.1 is that iOS 4.1 jailbreak is only for iPhone 3G and iPod Touch 2G (Non-MC) models. So if you have updated to iOS 4.1 and now want to downgrade to iOS 4, then follow the steps given below. Read this if you are looking to downgrade from iOS 4 to iOS 3.1.3 or iOS 3.1.2.
How To Downgrade iOS 4.1 to iOS 4, iOS 3.1.3 or iOS 3.1.2
Step 1: First of all to downgrade from iOS 4.1 to iOS 4 you need the firmware (IPSW) file. After you have got hold of the required IPSW file, you need to put your iPhone/iPod Touch in DFU mode. Keep in mind that DFU mode is different than recovery mode.
Step 2: To put your iPhone/iPod Touch into DFU mode, first make sure that iTunes is running on your PC. After that switch off your iPhone/iPod Touch and press the Power and Home button on the device together to put your device in DFU mode.
Now connect your iPhone/iPod Touch to your PC using the USB cable. After 10 seconds or so, release the power button whilst holding the Home button. At this point, iTunes should recognize a new USB device, which will be identified as your device after a few seconds. If you have successfully put your phone in DFU mode, then your device screen will display a totally black screen.
Skip to step 4 if you own a iPhone 3G/iPod Touch 2G (Non-MC)
Step 3: This step is only iPhone 4, iPhone 3GS and iPod Touch 3G/2G (MC) owners. Now Users need to use the SHSH blobs of the iOS4 firmware. If you don’t have an SHSH blob of the iOS 4/iOS 3.1.3/iOS 3.1.2 firmware, then you are out of luck. Read this tutorial on how to make a backup of iOS4 SHSH Blobs.
Now users need to edit the hostsfile on their PC by going to c:\windows\system32\drivers\etc\. Open this hostsfile in Notepad and add the line below to the end of the document:
Now save the file and you are done. Keep in mind that you need to open the hostsfile in administrator mode to make changes to it.
Step 4: Now users need to restore the firmware they downloaded in Step 1 to their iPhone/iPod Touch. To do so, press the Alt key and click on the Restoreoption in iTunes. iTunes will then prompt you to point it to the IPSW file. Select the iOS 4 iPSW file and click on Open.
After this iTunes will do all the work for you. While restoring to the iOS 4 firmware, iTunes might throw in a 1011, 1013 or 1015 error. Just ignore these errors. At the end of the process, the firmware has been successfully restored to your iPhone/iPod Touch device.
5) Now all you need to do is to make your device exit from the Recovery Mode. To do so, users need to download a program called RecBoot. Run that program and just select the Exit Recovery Modeoption and you are done. Your iPhone/iPod Touch will restart on its own and it will now be running on iOS 4.