DFU means Device Firmware Update. If a restore using Recovery Mode doesn’t work you will want to use DFU Mode as a last resort. When placing your iPhone into DFU Mode it does not load the OS before attempting the restore
DFU mode as opposed to Recovery Mode, requires a bit of timing and can take practice so if at first you don’t succeed, don’t be afraid to keep trying.
•Plug your iPhone, iPod touch, or iPad into your Mac or Windows PC and make sure iTunes is running.
•Hold down both the Sleep Button (on top of your device) and the Home Button (on the front underneath the screen).
•Keep them both held down from about 10 seconds. (If you see the Apple logo, you’ve held them too long and will need to start again.)
•Let go of the Sleep Button but keep holding the Home Button for about 5 seconds. (If you see the “Plus into iTunes” screen than you held it too long and will need to start again.)
•If the screen stays black, that’s it! Your iPhone, iPod touch, or iPad should now be in DFU mode.
Remember, we are not RESPONSIBLE for any damage. Please read the instructions very well.