DFU Mode -- AKA "Don't F*ck Up" Mode

Just the other day, our assistant comptroller was downloading Circulate (on his iPhone) and all of a sudden the App Store crashed and the white Apple Logo appeared. No big deal, right? This happens all the time (which is another story altogether) so he sat and waited, and waited and waited... but the white logo never went away. He tried to turn his phone off--no luck. He tried a hard reset (holding down the power button and home button until the white logo appears) and although the screen went black for a second, when the logo reappeared, it never went away. By never, we mean that he could not turn off his phone... eventually, the battery died, and the white logo was replaced by the red empty battery logo.

Being an industrious employee of iPhonePOV.com, he decided to plug his iPhone into his computer and have iTunes fix things. That didn't work either. Although iTunes could see his iPhone, he could not sync and the white logo remained. Double-hmmm. Having no other recourse, he decided it was time to "restore" his iphone to its virgin state. So he pushed the "restore" button in iTunes and after a few moments was greeted with a error message "Cannot restore this iPhone (error 1621)" After a long Google session, he realized that there is no information on the Internet about iPhones that will not shut off and receive error 1621 when restoring. This left only one option... the Genius Bar at his local Apple Store. So, he made an appointment, brought in his iPhone and told them the story of his troubles. And that's when the told him about the top-secret DFU mode.

Turns out his is not the only iPhone to exhibit this behavior. It happens all the time, but, there's a secret DFU mode that will save the phone and a trip to the Genius bar. Here's what you do.

Plug in your iPhone with the USB cable and open iTunes. Then, hold down the power button and the home button... when the iphone resets (after 5 to 10 seconds...) let go of the power button (the one on the top edge) and continue holding done the home button. Keep holding the home button and eventually iTunes will ask you if you want to restore your phone. Say yes.

Turns out this DFU mode restore is different than a normal restore... it's a low-level firmware restore, which can fix many problems that can't be fixed by a run-of-the-mill restore.

The "Genius" also suggested his iPhone crash may have been caused by a bit of corruption in a specific application's DRM. His suggestion was to re-download all of his applications (through iTunes) and then re-sync the newly downloaded applications onto the iPhone. This is a time consuming endeavor, but if you're having lots of iPhone crashes and/or your phone keeps resetting, it might be worth trying.