Unbrick HTC One – HTC black screen with warning signs on edges

Today I had a problem while trying to return to stock my HTC One: I ended up having this HTC RUU Mode screen with warning logos on the edges and I found no way to get out of that; rebooting, even with VOL – pressed, brought me to that screen. I thought it was bricked, but don’t worry, there’s a solution!

My phone was S-ON and LOCKED, and it had a wrong CID: was set to HTC__405, which was not it’s original one, so I thought that there was a very little chance to recover it; however it can be done and it’s pretty simple (once you know what to do 😀 ).

I found out that, on that screen, fastboot OEM commands work. That doesn’t bring us directly to a solution, but it’s enough to start with!

What we need:

• a stock RUU – pick one 😀
• HTC Drivers – install HTC Sync, then let it recognize your phone in fastboot mode, then remove HTC Sync leaving HTC Drivers installed
• fastboot executable – here you are executables for Windows, Linux and OS X. To follow this guide, rename the right one to fastboot, removing the operating system name.

There are some issues with Windows 8.1 and fastboot; if you have an Intel USB 3.0 controller, here’s the fix; otherwise, you have to use a computer with another OS. I used Windows for the RUU but I’m quite sure it can be flashed via fastboot aswell.

Let’s start!

• on a command prompt, move to the fastboot folder with the cd command.
• the first thing to do is to unlock the phone using the HTCdev method. Just register and follow the instructions to unlock the bootloader.
  You will be asked to confirm on your phone; the screen will not display the menu as it should, but you can do that by just pressing VOL UP and then the POWER button. The phone will reboot. Now we are S-ON but UNLOCKED, that’s a little step ahead.
• we can boot into the system with the command
  

  fastboot oem boot

  It’s not a solution since on the next reboot, we’ll be back to the HTC black screen, but we have to do that now because the next goal to achieve is S-OFF. The system will boot as normal, just skip all the setup because it’s going to be reflashed soon.

• now, if we enable USB Debugging, we have an ADB shell. That means we can S-OFF our phone with the given tools. If the installed HBOOT is 1.44 use Revone, if 1.5 or higher use Rumrunner. There are other tools too, as far as I know almost any HBOOT can be S-OFFed right now.
  S-OFF procedures may require several reboots and working with fastboot and ADB (Revone just a single reboot, Rumrunner some more).
  Of course, to switch from ADB to fastboot just let it reboot, to switch from fastboot to ADB you have to run the fastboot oem boot command since the phone will reboot into fastboot itself.
  When Rumrunner waits for ADB, open another console and run this command to force the phone to boot the OS (and then, ADB).
• now our HTC One is both S-OFF and UNLOCKED! We have to set our CID to 11111111 to allow the flash of the downloaded RUU (not needed if the downloaded RUU matches your current CID).
  To set the SuperCID, boot into fastboot mode (the “normal” black HTC screen we are now used to). Then type the command

  fastboot oem writecid 11111111
  fastboot reboot

• Now the easy part, just run the RUU you downloaded before. It will install without issues thanks to the SuperCID, and the phone will, eventually, boot as normal into Android.

Good luck!
You may want to upgrade your system or tweak the HBOOT (red warning and tampered text), but if you bricked your phone this way, i’m sure you already know what to do 😀