Connect the iPhone to your computer using a USB cable.
Press and hold the Sleep/Wake and Volume Down buttons at the same time for exactly 10 seconds.
Release just the Sleep/Wake button and continue pressing the Volume Down button until iTunes pops up with a message telling you that it’s detected an iPhone in recovery mode.
The iPhone’s screen will remain black. If you see an iTunes logo displayed you are in recovery mode not DFU mode. Give it a try again and make sure you pay close attention to the timing.
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