My HTC One X came with ICS pre-installed, but then I upgraded it to Android 4.2.2 using CyanogenMod. Now I want to reset my phone to its original ROM, but couldn't find a way to do it.

Someone suggested that I download and run:


but it didn't work. When I run the .exe I get the error:

 Error[155]: UKNOWN ERROR

My bootloader shows its version as:

(bootloader) DEBUG: cid: VODAP001
*** UNLOCKED ***

How can I get the stock ROM reinstalled?

  • Where did you run the .exe file? If directly on the Android device, this would explain the error. It's most likely a Windows executable / self-extracting archive.
    – Izzy
    Commented May 24, 2013 at 18:28

1 Answer 1


This is a protection that HTC uses to ensure quality in their devices. To re-install their custom stock, you must re-lock your phone. To do this, place your phone into fast-boot mode and plugin in via USB:

At the command line (or wherever you may have the fastboot binary), execute these commands:

fastboot devices
fastboot oem lock

This will lock your bootloader and allow you to run the RUU. Your device should now report "LOCKED". After your device is locked, proceed with running your *.exe on Windows.

(Make sure you're installing the right one first!) List of RUU's: http://androidfiles.org/ruu/?developer=Endeavor

Full Tutorial: http://androidforums.com/one-s-all-things-root/691874-guide-how-run-ruu-your-htc-one-s.html

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