Sony Xperia U (ST25i): Performance issues after updating to Android ICS (4.0.4) using the official method

I have noticed my household’s Xperia U (ST25i) slowed down quite a lot after upgrading to ICS (6.1.1.B.1.54-Stock Version), using the official method provided by Sony.

I do not want to have the phone rooted at the moment, so wanted to ensure I would find a solution without requiring such thing. And I just did.

Here’s how to bring your Xperia U up to speed again:

WARNING: I am not responsible for any problems that may occur after you follow the instructions below. Do not proceed unless you’re absolutely sure that you know what you’re doing. Proceed at your own risk. You have been warned.

    1. First and foremost, check your android version and build number (go to “Settings” -> “About Phone”). They must be “4.0.4” and “6.1.1.B.1.54”, as that is the package being distributed by Sony in Europe, at least at the moment. So if you have upgraded your phone to ICS through the official method, those versions should match.
    2. Download Flashtool, it’s available here.
    3. Download the World-Unlocked Kernel Firmware File, it’s available here.
    4. Install FlashTools (install to C:\Flashtool).
    5. Install the Flashtool drivers. To do this, execute the file”Flashtool-drivers.exe”, which should be located at “C:\Flashtool\drivers” in your computer.
      Under “Components to install”, check the following items:

      • Xperia P, Xperia U and Xperia sola drivers
      • Flashmode drivers
      • Fastboot drivers

      Click the “Install” button and let it run. The installer will execute “dpinst32.exe” (Windows Driver Package Installer) on the final stage. Make sure you complete the process there, and do not freak out once you see the “Untrusted/Unsigned” driver installation warning – make sure you allow it, as you do need the drivers for the process to work, and they’re harmless anyway. Once you complete the installation of the drivers on the “Driver Package Installer” window, the Flashtool driver’s setup will resume and tell you that the installation process is complete.

    6. Extract the file “xperia u_6.1.1.B.1.54_World kernel.ftf” from the archive you downloaded ( to the folder “C:\Flashtool\firmwares”.
    7. Enable “USB Debugging” on your phone by going to “Settings -> “Developer Options”. It should be the very first option of that screen. Once “USB Debugging” is enabled, you should see a new icon on your phone’s task bar (the top one), reminding you of that fact.
    8. Connect your Xperia U to the computer and give it time to install its drivers (Windows should notify you during the process or show an icon in your taskbar)
    9. Start Flashtool as an administrator (just to make sure). You can do this through the start menu or by browsing the “C:\Flashtool” folder, then right-clicking “FlashTool.exe” (or just “FlashTool” if your Windows is not setup to show file extensions) and selecting “Run as Administrator”.
    10. Click on the very first button in the Flashtool interface (“Flash”) and then select “Flashmode” on the mode selector.
    11. You should now have the “Firmware Selection” window in front of you. Unless you did not copy the firmware file to the “firmwares” folder, you should see it listed under “Select a Firmware”. The version you need to select is “6.1.1.B.1.54“. Once the version is selected, click on “OK” button.
    12. Flashtool will now shutdown your phone and ask you to connect it in “Flash Mode”. To do so, just press and hold the “Volume -” key, and while holding it, press the power button. Flashtool will recognize that the phone is in flash mode, and will carry on with the rest of the process.
    13. Flashtool will now show the message “Please unplug and start your phone”. This means exactly that, disconnect the phone from your computer, and power it on. Your phone’s performance should now be back to what you were used to, while still running Android 4.0.4 (ICS)!

The Flashtool log should look like this (or similar):

07/038/2013 18:38:42 - INFO  - Device connected with USB debugging on
07/038/2013 18:38:45 - INFO  - Connected device : ST25
07/038/2013 18:38:45 - INFO  - Installed version of busybox : N/A
07/038/2013 18:38:45 - INFO  - Android version : 4.0.4 / kernel version : 3.0.8+ / Build number : 6.1.1.B.1.54
07/046/2013 18:46:50 - INFO  - Device connected in flash mode
07/046/2013 18:46:52 - INFO  - Device disconnected
07/049/2013 18:49:04 - INFO  - Selected xperia u_6.1.1.B.1.54_World kernel.ftf
07/049/2013 18:49:04 - INFO  - Preparing files for flashing
07/049/2013 18:49:04 - INFO  - Please connect your device into flashmode.
07/049/2013 18:49:15 - INFO  - Device connected in flash mode
07/049/2013 18:49:15 - INFO  - Opening device for R/W
07/049/2013 18:49:16 - INFO  - Reading device information
07/049/2013 18:49:16 - INFO  - Phone ready for flashmode operations.
07/049/2013 18:49:16 - INFO  - Current device : ST25i - 6.1.1.B.1.54 - WORLD_6.1.1.B.1.54
07/049/2013 18:49:16 - INFO  - Start Flashing
07/049/2013 18:49:16 - INFO  - Processing loader
07/049/2013 18:49:16 - INFO  -     Checking header
07/049/2013 18:49:16 - INFO  -     Flashing data
07/049/2013 18:49:17 - INFO  - Loader : S1_Root_3065 - Version : R5E006 / Bootloader status : NOT_ROOTABLE
07/049/2013 18:49:17 - INFO  - Processing kernel.sin
07/049/2013 18:49:17 - INFO  -     Checking header
07/049/2013 18:49:17 - INFO  -     Flashing data
07/049/2013 18:49:20 - INFO  - Ending flash session
07/049/2013 18:49:20 - INFO  - Flashing finished.
07/049/2013 18:49:20 - INFO  - Please unplug and start your phone


NOTE: This procedure will NOT root your phone.
It will just correct the performance issues (slowness) that everyone is talking about. 🙂

9 Responses to “Sony Xperia U (ST25i): Performance issues after updating to Android ICS (4.0.4) using the official method”

  • Happy camper:

    I don’t know what these steps do exactly, but my phone is like new again. I can’t believe I put up with the slowness for so long. Thanks so much!

    • Hi there,

      Thanks for letting me know it worked, and you’re very welcome!
      What you did there was basically to replace the kernel, which is pretty much the brain of the system.

      (You replaced it with the “World Unlocked” version of it, which is the kernel included on the latest versions of ST25i’s that are unlocked and sold through retail channels all over the globe. Those new ST25i’s are shipped with Android 4.0.4 by default, and they work fine. This is where I got the idea to replace the kernel, pretty much a shot in the dark but it ended up working.)

      Enjoy the “new” system!

  • Barbara:

    Hello! From step 12) nothing happens… I shutdown my phone and pressed Volume – while pressing power button (it entered safe mode) but flashtools didn’t recognize nothing , what should I do?
    (sorry for the bad english)

    • Barbara:

      04/025/2014 14:25:30 – INFO – Please connect your device into flashmode.
      04/026/2014 14:26:54 – INFO – Device connected in flash mode
      04/026/2014 14:26:55 – INFO – Opening device for R/W
      04/026/2014 14:26:55 – INFO – Start Flashing
      04/026/2014 14:26:55 – INFO – Processing loader
      04/026/2014 14:26:55 – INFO – Checking header
      04/026/2014 14:26:55 – INFO – Ending flash session
      04/026/2014 14:26:55 – ERROR –
      04/026/2014 14:26:55 – ERROR – Error flashing. Aborted

      • Hello Barbara,

        Quick question: Did your phone start in safe mode when you held “Volume -” and pressed the power button? The phone is supposed to enter safe mode by then and not to boot normally. I assume you’ve seen a different screen there, but if not please let me know as that might be the issue (it might just not be booting into the flash mode).

        So, assuming that the phone booting part is alright… I am tempted to “guess” that one of the following steps wasn’t completed successfully/correctly:

        Step 5: If this step isn’t performed correctly, the computer won’t “see” your phone correctly (it will still detect it, but it will use the wrong drivers). As such the application won’t use the good drivers neither, and the process will fail.
        Step 7: If USB Debugging isn’t enabled on your phone, communication will will be restricted to “user mode”, so it’s important to ensure it’s properly activated.
        Step 8: It’s common for Windows to be slow in this process. Give it enough time and wait for a completion message.

        Before going ahead and trying again, I highly recommend you to:

        1) Use another USB port this time (so that the previous drivers are not mapped to it) — if you are short on USB ports, a USB-Hub with multiple ports will also work fine.
        2) Reboot your computer after the Step 5. Once your computer is back on the operating system, continue from step 6.
        3) Reboot again after the Step 8. This is just to make sure Windows loads the proper drivers. (Rebooting will force everything to reload). After that, continue from Step 9.

        Good luck and let me know how it goes!

  • Eduardo Melo:

    My st25i, which is now my wife’s phone, had 4.0.4 flashed by me. It lagged like hell. Anyway, got it rooted, got the ramdisk for launching cm kernel… Flashed firecyano, miui, tins of custom roms and it always had some issues (modules such as wifi and Bluetooth missing and so on). So I went back to the drawing board… Flashed the second to last version, flashed only the last version rom, rooted the damn thing, flashed latest kernel. It was lightning fast! But not for me…
    Had written a custom build.prop, with some help, and guess what?
    Worked just fine!
    Anyway, it’s a piece of crap… L.Bootloader…

    Keep Rocking

  • Rob:

    Thanks for the clear guide, however I have not attempted it on my phone because my build number is NOT 6.1.1.B.1.54, even though I have checked for the newest update right now it still says that my 6.1.1.B.1.10 build is up to date.

    Would this be an issue if I do this procedure?

  • abid:

    Hi dear
    My xperia u build number is 6.1.1.C.1.0 and it has T Mobile version can i use above mathod??

Leave a Reply