How to Downgrade iOS 4.1 to iOS 4.0 iPhone Firmware

Apple iOS 4.1 firmware for iPhone 3G, 3GS and iPod Touch 2G and 3G is already out for download. Before updating your iOS firmware to 4.1 you must save SHSH Blobs (ECID SHSH) files to Cydia first so that you can jailbreak your iPhone on iOS 4.1 as well. After installing iOS 4.1, you will surely lose your jailbreak and ultrasn0w software unlock on your iPhone and iPod Touch, and being latest firmware you might face incompatibility issues with your favorite iPhone apps forcing you to return to old iOS 4.0 firmware. If you are looking for a solution to downgrade iOS 4.1 firmware to iOS 4.0 then follow the steps below (for Windows and Mac users).

VERY IMPORTANT: This process is only for those who have already saved the ECIDs with SHSH to Cydia Server.

STEP 1: Modify the Host file:
Windows

• Open Notepad with administrator privileges and then right click on the icon of notepad and click on “Open as administrator”
• Now that Notepad is open Go to folder C:/WINDOWS/system32/drivers/etc and open the file
• Add the following line at the end of the document and save it: 74.208.10.249 gs.apple.com

Mac

• Navigate to Go -> Go to Folder and enter the path /etc
• Open the file hosts with TextEdit, add the following string 74.208.10.249 gs.apple.com and save the file to your desktop.
• Now return to the previous folder by following the same method and copy the text within this file by replacing the original file (If prompted for a password enter it and click OK)

Requirements

• iTunes 9.2
• Original firmware 4.0
• iRecovery v 1.3 for Mac
• Libusb library for Mac
• iRecovery libusb 1.3 + for Windows

How to downgrade iOS 4.1 iPhone firmware to iOS 4.0 [Mac OS]

Step 1 Copy the application ”iRecovery” on the desktop and install the library “libusb”. Windows 7 or Windows Vista users, who can not run the libusb and only getting malfunction of all USB ports), a fix is available through which you can bring the iPhone in Recovery Mode. Just follow the steps listed here.

Step 2 Open iTunes, click the ALT key + Restore and manually load the original 4.0 firmware.

Step 3 During the restore process, you’ll notice a pop up with error 1015, neglect it.

Step 4 Click Ok to close the pop-ups and close iTunes.

Step 5 Now open the terminal and type the following commands:
cd Desktop
./iRecovery-s
 setenv auto-boot true
 saveenv
 fsboot
 exit

Step 6 Wait a few seconds and disconnect the iPhone from the cable, then reboot the phone by clicking Home + Power buttons simultaneously.

Step 7 Once you connect the phone via USB and proceed normally, the Apple logo appears on the display.

 Voila! The downgrade from iOS 4.1 to iOS 4.0 is successfully completed.

How to downgrade iOS 4.1 iPhone firmware to iOS 4.0 [Windows]

Step 1 Extract the archive iRecovery and bring the application on your Desktop.

Step 2 Install “libusb-win32-filter-bin-0.1.12.1.exe” and keep the file on the desktop.

Step 3 Connect your iPhone via USB and put it in DFU mode (hold down the button “Power” and “Home” for 10 seconds then release).

Step 4 Restore and manually load firmware 4.0 (by pressing Shift + Restore and select the firmware you downloaded previously).

Step 5 Towards the end of recovery, the procedure will stop and return the iTunes error 1015. Neglect it.

Step 6 Click OK on the pop-up, Close iTunes and run the console by typing the following commands:

cd Desktop (or folder where you copied iRecovery)
iRecovery.exe-s
setenv auto-boot true
saveenv
fsboot
exit

Step 7 Unplug the iPhone from your computer and restart it by pressing the Power and Home until the Apple logo appears. Once turned on, connect to your computer, activate it and use it normally.

Voila! The downgrade from iOS 4.1 to iPhone iOS 4.0 is successfully completed.

While downgrading iOS 4.01/iOS 4.1 to iOS 4.0, 3.1.3 firmware or trying to restore to custom firmware you might stuck with error 1015 in iTunes. To fix or troubleshoot error you may try the following guides:

• Fix iPhone Restore Error Code 3194, 1015 from iOS 4 to iOS 3.1.3
• Error 1015 Fix: Solving the iTunes error 1015
• Put iPhone and iPod Touch in Recovery Mode with RecBoot

You might also Like to check out more on iOS 4.x, 3.1.3 Jailbreak and baseband unlock:

• iDetector: Find Bootrom Version for iPhone 3G/3GS iOS 4 Jailbreak
• Jailbreak iOS 4.0 iPhone 3GS/3G, iPod Touch 3G/2G [new iBoot] with Sn0wBreeze
• How to Jailbreak iOS 4 on iPhone 3G, 3GS and iPod Touch 2G with PwnageTool 4.0
• Unlock 05.12.01, 04.26.08 to 05.13.04 Baseband on iPhone 3GS/iOS 4 with ultrasn0w 0.93
• Jailbreak iPad, iPhone and iPod Touch OS 3.1.3 with Spirit on Windows, Mac, Fix Errors