Earlier today we told you how to downgrade your A4 iOS device from the iOS 5.1 firmware to the iOS 5.0.1/iOS 5.0 firmware. The reason someone would want to downgrade their iPhone, iPod Touch or iPad back to a lower firmware version is if they would like to be able to Jailbreak again, or want to be able to Jailbreak Untethered.

For those of you who would prefer to downgrade from the iOS 5.1 firmware to the iOS 4.3.5/4.3.3/4.x firmware you will be glad to know it is possible. And as such in this how to guide from iJailbreak.com you will learn how to downgrade your iOS device from iOS 5.1 to the iOS 4 firmware generation. Before we start however make sure you meet the requirements listed below…

iOS 5.1 Downgrade Requirements: 

  • Supported iOS devices include the iPhone 4, iPhone 3GS, iPad 2G, iPad 1G, iPod Touch 4G, iPod Touch 3G. Unsupported iOS devices include the iPhone 4S.
  • Saved SHSH blobs for the iOS 4 firmware you plan to downgrade to.

Downgrade iOS 5.1 To iOS 4.3.5/4.3.3/4.x

Step 1) – The first thing you will need to do is download the latest version of RedSn0w for your Windows or Mac OS X computer. This can be done by going to the iJailbreak Downloads Section or using on of the direct links below.

Download RedSn0w 0.9.10b6 (Windows)

Download RedSn0w 0.9.10b6 (Mac OS X)

Step 2) – With RedSn0w downloaded you will need to launch it, click the Extras button and then click the Pwned DFU button. Upon clicking the Pwned DFU button you will simply need to follow the instructions presented to your for putting your iPhone, iPod Touch or iPad into pwned DFU mode.

Downgrade iOS 5.1 To iOS 4.x

Step 3) – Once your iOS device is in pwned DFU mode you will need to trick iTunes into thinking that it is connected to Apple’s servers, while really it will be connected to Saurik’s servers. To do this you will need to edit the hosts file, which involves a slightly different procedure whether you are following this how to guide from a Windows or Mac OS X computer.

Windows Instructions 

For Windows users you will need to navigate to the following directory:

C:\Windows\System32\drivers\etc\

From this directory you should see a file called hosts. Back this file up to your desktop or another safe location and then open it in Notepad.

Mac OS X Instructions

For Mac OS X users you will need to navigate to the following directory:

/etc/

From this directory you should see a file called hosts. Back this file up to your desktop or another safe location and then open it in TextEdit.

Step 4) – With the hosts file open in a text editor on your Windows or Mac OS X computer you will need to add the following line at the end:

74.208.105.171 gs.apple.com

Once the line has been added you can save the file.

Downgrade iOS 5.1 To iOS 4.x

Step 5) - You will now need to launch iTunes and restore your iPhone, iPod Touch or iPad to the iOS 4 firmware file you are downgrading to  (download iOS firmware files here). This can be done by Option (alt) clicking the Restore button on Mac OS X or by SHIFT clicking the Restore button on Windows.

Downgrade iOS 5.1 To iOS 4.x

Step 6) – When iTunes Error Code 10xx pops up you will simply need to use a tool like TinyUmbrella (download here) to kick your iOS device out of recovery mode. Once it has been kicked out of recovery mode you have successfully downgraded your iPhone, iPod Touch or iPad from the iOS 5.1 firmware to the iOS 4.x firmware.

Congratulations! The process is now complete and you can re-Jailbreak your iOS device by going to iJailbreak’s How To Jailbreak section. Please leave any further questions in the comments section.

Update #1: Learn how to fix iTunes Error 3194 by clicking here.