Steps to Put iPhone into DFU Mode

DFU (Device Firmware Upgrade)mode bypasses the current OS installed and allows you to upgrade or downgrade your OS. If you are getting errors trying to restore in iTunes, DFU mode is very likely for you.

This article shows you the steps to put iPhone into DFU Mode.

To put the iPhone into DFU mode so you can do an iTunes firmware restore follow these steps:

Step One
Open iTunes and connect the iPhone to your Mac.

Step Two
Press and hold the Home button and the Sleep/Wake button at the same time.

Step Three
After exactly 10 seconds release the Sleep/Wake button. Continue holding the home button until you iTunes pops up a message telling you that it has detected an iPhone in recovery mode.

The iPhone screen will remain black like this:

NOTE***: It may take a few attempts to get your iPhone into DFU mode. Generally, I hold down both buttons then release the Home button just before I think the Apple logo would appear. If you are still holding both buttons down and you see the Apple logo you are holding them down for too long!

Source From:http://www.iclarified.com/