I have an Xperia Z and recently I unlocked the bootloader. However now I cannot install (upgrade) to the Lollipop Android 5.0 (10.6.A.0.454) from Android 4 (10.5.1.A.0.292) through the Sony website. I always get the message "cannot be installed because I have an unlocked bootloader".

Please advise on a step by step process to lock the bootloader again if possible or advise on how to upgrade to 5 version.

Please make it for dummies because I am not experienced or a developer whatsoever.


Actually it's possible to relock the bootloader, using Flashtool. The process can be found on this XDA Forum post.

  1. Download Flashtool from www.flashtool.net
  2. Start Flashtool and click on BLU button
  3. You will be asked to connect device in flash mode
  4. Once you connect the device you will get a prompt to "Relock"
  5. Click on it and when prompted disconnect the device

You should download the custom version of the ROM from some trusted source and then flash it from your boot loader.

Don't forget to take backup of your current configurations. And I recommend you to install some custom recovery as well (like teamwin recovery).

NOTE: Before using this method, take backup of your device.

  • Note that this will require you to clear your data from the device.
    – onik
    Aug 22 '15 at 18:05
  • Of course this will. You will have to take backup of your device.
    – Panda
    Aug 23 '15 at 2:09

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