Update Xperia U ST25i to Android 5.0.2 Lollipop With CM 12 Custom ROM

Previously we posted a guide to update Xperia U to Android 5.0.2 Lollipop using OmniROM custom ROM. In this guide, we bring the CyanogenMod 12 based custom ROM to update Xperia U to Android 5.0.2 Lollipop. There are lot differences between CyanogenMod and OmniROM and there is a big user fan base for both of these custom ROMs. Both of these custom ROMs are WIP and supported by developers. Both ROMs receive weekly updates. Users can try both ROMs and choose the best one for themselves. This CM 12 custom ROM is for Xperia U ST25i only. It should not be installed on any other smartphone or variant of Xperia U. It is based on stock Android, stock Android users will find it better for use. All the steps involved in installing this custom ROM on Xperia U are given below. Make sure that you follow every step to avoid any blockage during installation.


  • Unlock Bootloader of Xperia U. If you do not know how to do it or you have no idea about what it is, then follow this guide to unlock Bootloader of your phone. How to Unlock Bootloader of Xperia Smartphones
  • Install USB Drivers for Xperia U using the drivers installer from the Flashtool installation folder. Download Flashtool from here. After installing USB Drivers, connect phone to PC using the USB cable so that USB drivers are installed properly and connection is established properly.
  • Install ADB and Fastboot Drivers. | Mac ADB And Fastboot Drivers. To avoid the lengthy installation, use the Minimal ADB and Fastboot tools for your PC to make the installation quick. ADB Drivers work best on Windows 7. ADB and Fastboot Drivers might not work on Windows 8 or Windows 8.1.
  • Charge your phone up to 50%. It is very important because phone should not turn off during flashing process. If the phone turns off during the flashing process, it can damage the device.
  • Make a backup of all Contacts and Messages on phone. – Guide
  • Backup SMS Messages
  • Backup Call Logs
  • Make a Nandroid Backup if any custom Recovery is installed already. If not, you will find a custom recovery later in this guide. – Guide
  • Copy all the media files and anything else stored in the internal memory to a PC before flashing to save this data.


The methods involved in flashing custom recoveries, ROMs and rooting your phone are highly custom and may result in bricking your device, and has nothing to do with Google or the device manufacturer that is SONY in our case. Also rooting your device will void its warranty and you will be no longer eligible for any kind of free device services by the manufacturers/warranty providers. In case of any mishap we may not be held responsible. Follow these instructions to the letter to avoid any mishap or bricking. Make sure that whatever you do, you are doing it at your own responsibility.

Required Downloads

Steps to Install CM 12 on Xperia U ST25i

  1. Make sure that bootloader is unlocked and phone is charged to 50% at least.
  2. Extract boot.img from ROM zip.
  3. Copy ROM zip and Gapps zip to phone’s internal memory.
  4. Now turn off phone wait for 5 seconds.
  5. Hold volume up button and connect phone to PC.
  6. The LED should remain blue, which means that phone is in fastboot mode.
  7. Now copy boot.img to Fastboot folder or Minimal ADB and Fastboot installation folder.
  8. Open that folder, hold shift button on keyboard and right-click on mouse.
  9. Click on Open Command Window Here.
  10. Type fastboot devices and press Enter.
  11. It should only one fastboot connected device in return. If it showing more that one, then disconnect any other connected device or close any Android Emulator. Also make sure that PC Companion is completely disabled if installed.
  12. Now type fastboot flash boot boot.img and press Enter.
  13. Type fastboot reboot and press Enter.
  14. While phone is booting up, press Volume up/down/power to enter recovery mode.
  15. In the recovery mode, select Install and navigate to the folder where ROM zip is placed.
  16. Install the ROM zip.
  17. Install Gapps zip the same way and reboot the phone.
  18. Performing factory reset and wiping Dalvik cache after installing ROM is highly recommended!
  19. The phone will boot up to home screen in 5 minutes.
  20. To install Google Applications, copy downloaded Gapps zip file to phone and flash it the same way as ROM. Factory reset is not required this time.
  21. That’s all!

Got any question? Ask me in the comments below 🙂

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Usama M

+Usama M: Ex Farmviller | Android Fanatic | Software Engineer,Founder - TechBeasts.com
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  • Ermelinda Carvalho Baltruillas

    Hello. I’m trying to install this rom on your cyanogenmod 11 rom for st25i I already installed before. Now, when I try to flash the kernel image there is an error in fastboot (0x05cf… ). What to you suggest to me? Installing cyanogenmod 12 with the old kernel of cyanogenmod 11???

  • Arzath Aariz

    i completly installed omni rom on my xperia u but i coudnt install gapps i again again tried sameway but recovery mode didnt work. now how to install gapps and how to go to recovery mode.?

  • PanDra~


    my xperia u got a new look got faster and more intresting UI but OTG is gonne and no matter which usb device i try to connect, phone shows no sign of it or just falsely informs that the battery is charging . I realy nead OTG so can you guys fix this?

    bravia engine is gone

    i couldnt make groups in wifi direct.. is it gone, too?

    hotspot sheild , vpn force &… doesn’t connect or work so in Persia i can’t use beetalk , line, (e.g facbok) &… with my phone and it’s bad for me

    i don’t care about other bugs but OTG, wifi direct and anti censorship apps are more than to be called bugs it’s actualy a malfunction
    again thank you for a beautiful ROM ^_^

  • @disqus_jz40lHMWxS:disqus
    We cannot guarantee anything about the custom ROMs. As these are totally a custom task which depends on the user to install or not, all we can do is to recommend you to go back to stock if the issues are irritating.

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