DFU mode means Device Firmware Update mode.This is a not same iPhone recovery mode.This mode wants to change iDevices firmware.When you want to jailbreak, your iPhone 3G or want to download and install Cydia this DFU mode very valuable to bypassing your normally iPhone 3G’s OS.
Short description about iPhone 3G
Apple iPhone 3G is one of the best iPhones by release by Apple company.The iPhone 3G also runs Apple’s iOS 4.2.1 operating system.It has a multi-touch display which is the sense by user’s fingertip contact.iPhone 3G is the second generations one.Release date is july 11.2008.It has 2 mega pixel camera.
You can follow these below steps to put your iPhone 3G into DFU mode.
01.Connect your iPhone 3G to your PC via USB data cable.
03.Turn off your iPhone 3G by pressing Power button
04.Front of the bottom of iPhone has Home key. Top of the iPhone 3G has the Sleep wake button. Both of Home and Sleep Wake button keep holding approximately 10 seconds.
05.Now you can only release Sleep Wake button ,with keep holding home button. Moreover, until “iTunes has detected an iPhone in Recovery Mode” message shows on your PC.
06. Now your iPhone 3G is recovering in DFU mode. It is very easy to identify your iPhone 3G in DFU mode. When the iPhone 3G screen became completely black, it means you’re in DFU mode.
Important. If you get any trouble ,when you try to put your iPhone 3G to DFU mode, you must reduce the time of keep holding Power (Home ) button and Sleep Wake up button together by 9 seconds 8 seconds and last 7 seconds.
Now you can upgrade your’s iPhone 3G firmware up to iOS 5.1.1. And also, you can use to jailbreak it with using Redsn0w 0.9.14b2 version. If you want to put your iPhone 3G in to DFU mode, while the jailbreaking with Redsn0w 0.9.14b2 version, you can follow above step guide. If you are using iPad 2, iPad 3 and iPhone 4S, you don’t want to follow above method to put DFU mode. Course those three iDevices automatically get into DFU mode, when you use to jailbreak your’s iDevices with Redsn0w 0.9.14b2 version.