Apple has just released iOS 4.0.2 to fix the PDF vulnerability which allowed Comex to jailbreak all iDevices running iOS 4.0 / 4.0.1 & iOS 3.1.2 with JailbreakMe. If you will upgraded to iOS 4.0.2 then you will loose your jailbreak and unlock. Only iPhone 3G and iPod Touch 2G(non-MC) users can jailbreak and unlock iOS 4.0.2 on their devices with Redsn0w and Ultrasn0w. As iOS 4.0.2 do not come with any baseband upgradation, so you can still downgrade to iOS 4.0 / 4.0.1 by following the step-by-step guide below and then re-jailbreak it using JailbreakMe.
Before continuing, make sure your have SHSH blobs saved for either iOS 4.0 or iOS 4.0.1 (both are same) for iPhone 4, 3GS, 3G and iPod Touch 2G, 3G. We have already explained in detail that why and how you can save SHSH blobs for iOS 4.0 / 4.0.1 for iPhone 3G and iPod Touch 2G.
Downgrade iOS 4.0.2 to iOS 4.0 / 4.0.1 on Windows & Mac
*Find all required download links at the end of post
- *If you want to downgrade your device from iOS 4.0.2 to iOS 4.0 then download the iOS 4.0 IPSW file respective to your device. If you want to downgrade your device from iOS 4.0.2 to iOS 4.0.1 then download iOS 4.0.1 IPSW file. After downloading the firmware file, place it on your desktop.
- Put your iPhone in DFU mode. Follow the steps below to put your iPhone into DFU mode:
- Start iTunes. Connect your device to your PC / Mac with the USB cable.
- Turn of your device completely.
- Now hold down the Home and Power button for exactly 10 seconds and after that release the Power button but keep holding the Home button until iTunes detect your iPhone / iPod Touch in recovery mode. Your iPhone or iPod's screen should be totally blank at this point.
- Edit Windows / Mac HOSTS file:
- Navigate to Start->All Programs->Accessories and then right click on the Notepad icon and choose Run as Administrator
- Now go to File menu in opened Notepad and choose Open or simply press Ctrl+O. Browse to C:\Windows\System32\drivers\etc and open HOSTS file.
- Once HOSTS file is opened, copy-paste the following line at the end of file as shown in the screenshot below
- Now again go to File menu and choose Save or press Ctrl+S.
- Click Go->Go to Folder and then enter path /etc
- Now open HOSTS file with TextEdit and add the following line with at the end of the file as shown in the screenshot below.
- Now go to File and choose Save As, uncheck If no extension is provide, use .txt and save the HOSTS file on your desktop.
- Now replace the original HOSTS file with the one you just saved on your desktop. Incase you are prompted for the password, just enter it and click OK.
- Once you have successfully edited your HOSTS file, open iTunes and click on the name of your device from the sidebar menu.
- On the summary page, hold down the SHIFT key on keyboard and press Restore button. You will be asked to choose the firmware file you want to restore, choose the respective(iOS 4.0 or iOS 4.0.1) IPSW file you downloaded in step 1. If you are a Mac OS X user, use the ALT+Restore combo to choose the firmware file.
- Now iTunes will restore the firmware files on your device. Your iPhone screen will show you the restore progress. Just incase iTunes throws errors with code 1015, 1013 or 1011, just ignore them. Once the restore process is completed, proceed to the step below.
- *Download Recboot, it is a free utility for Windows and Mac users which allows you to force your iDevice to exit from recovery mode with a single click. Click on the Exit Recovery Mode button to restart your device.

For Windows Users:
74.208.105.171 gs.apple.com

For Mac Users:
74.208.105.171 gs.apple.com



TIP: If iTunes throw error 1015 during the restore process, use the instructions here to fix the error.

Once you have downgraded to iOS 4.0 or iOS 4.0.1, use the following tutorials to jailbreak and unlock your device:
Jailbreak: Jailbreak iOS 4.0 / 4.0.1 on iPhone 4, 3G, 3GS & iPod Touch (1G, 2G, 3G)
Unlock: Unlock iPhone 4, 3G, 3GS iOS 4.0 / 4.0.1 With Ultrasn0w 1.1-1
Update1: Downgrade iOS 4.0.2 to iOS 4.0.1 on iPhone 4 & iPhone 3GS Without SHSH Blobs
Download Links:
Download iOS 4 for iPhone 4/3GS/3G, iPod Touch 2G/3G – Final Version
Download iOS 4.0.1 for iPhone 4, iPhone 3GS and iPhone 3G
Download iTunes 9.2.1 for Windows and Mac
Download Recboot for Windows and Mac

