Unbrick a Bricked Zenfone 2 ZE550ML/ZE551ML (Restore Bootloader)

Installing custom recovery, custom ROM, custom kernel and enabling root access on your Zenfone 2 are fine, but if you have not followed the instruction carefully, you might end up with a non-booting system. This situation is called soft bricked, which is hard to recover as it damages the bootloader.

Because of damaged bootloader, you will not be able to use ADB and fastboot command to restore the stock ROM on your Zenfone 2. However, you do not need to worry. You can unbrick a bricked Zenfone 2 (ZE550ML/ZE551ML) with a tool called xFSTK and restore stock ROM using ASUS FlashTool.


The xFSTK tool is a windows application that lets you restore damaged bootloader on your Zenfone 2 (ZE550ML/ZE551ML). After restoring bootloader, you can use Asus Flashtool to install the stock ROM.

Thanks to XDA user Sumit007s, in this guide, we will explain how to unbrick a bricked Zenfone 2 (ZE550ML/ZE551ML) by restoring lost bootloader on it. The below method requires little technical expertise. Read the guide carefully before proceeding.

How to Restore Bootloader on Zenfone 2 (ZE550ML/ZE551ML)

Disclaimer: Follow the instruction at your own risk. Ensure that your device is soft bricked before proceeding. We will not be liable if any damage occurs to your device and/or its components. It is recommended for technically talented users only.

1. Download IntelSocUSB driver [HERE] and install it on your Windows PC. Switch off Zenfone 2, then press Power + Vol up key together few seconds and then connect it to your computer via a USB cable.

2. Download xFSTK Downloader (v1.7) [HERE] and install it on your PC. This tool is used to restore bootloader into the memory chip.

3. Now, download required files for Zenfone 2 ZE551ML [HERE] and for Zenfone 2 ZE550ML [HERE] and unzip the content to a folder. You will get three files: dnx_fwr.bin, ifwi.bin and bootloader.

4. Open xFSTK Downloader tool and select ‘MRD tab A0 / B0 + A0 + CRC….’ tab.

5. Click ‘Options’ and then click ‘Modify Settings’. Enable the box ‘GP Flag Override’ and set the value to 0x800000807. Click OK to proceed.


6. Click FWI DnX box and add the file dnx_fwr.bin (you have unzipped in step 3) Then, click IFWI and add the file ifwi.bin. Then click OS Image and add the bootloader file (droidboot_dnx.img.POS_sign.bin). After adding three files click ‘Begin download’ button.


[If your Zenfone restart, long press the power key to shut it down and then click power key to begin download]

7. When the process is completed, you will see ‘Success: FW+OS download complete’ message in the tool and your phone will boot into fastboot mode.

Now you have successfully restored bootloader on your Zenfone 2. You can now use Asus Flashtool to restore stock firmware on it. We will explain the procedure in the next post. (Source – Sumit007s)

Kannan is a computer and Android enthusiast, a blogger by passion and a tech freak. His always ready-to-help attitude, knowledge and hard work is what drives him.


  1. Wang Sherpa

    Sep 28, 2017 at 4:04 pm

    Guys use the xfstk files of ze551ml for ze550ml … It’ll work and then flash raw file and img files…

  2. Kirit Khant

    Jan 30, 2017 at 2:52 pm

    My bootloader is bricked after flashing files of mashmallow. This method can’t work for me. It stucks after….
    18:52:50 – XFSTK-STATUS–Firmware download completed. Continuing to OS…
    18:53:00 – XFSTK-STATUS–Reconnecting to device – Attempt #1
    18:53:01 – XFSTK-STATUS–Reconnecting to device – Attempt #2…..

    Even Phone does’t vibrate when I restart it. What should I do ???

    • lroe

      Mar 3, 2017 at 7:03 pm

      i’ve got the same problem bro, have you bring your zenfone 2 back to life ??

      • Waltham

        Mar 23, 2017 at 11:09 am

        Same issue. Firmware goes OK but OS doesn’t. Mine seems to “turn off” just before the OS process starts, therefore it can’t reconnect to it. If a turn it on while it’s “Reconnecting to device”, it starts over with the Firmware process and gets stuck again at the OS step.
        I then unplug it and plug it to the wall, it keeps doing the same two vibrations every some minutes.
        How to proceed?

        The log:
        01:54:59 – XFSTK-LOG–FW: Firmware update completed…
        01:54:59 – XFSTK-LOG–LogProgress
        01:54:59 – XFSTK-LOG–LogProgress
        01:54:59 – XFSTK-LOG–LogError
        01:54:59 – XFSTK-STATUS–Error Code: 0 – Success
        01:54:59 – XFSTK-LOG–void MerrifieldDownloader::do_abort()
        01:54:59 – XFSTK-LOG–Abort
        01:54:59 – XFSTK-LOG–D:/Downloads/201703 Zenfone/rescue/rescue/xFSTK_ZE551ML-sal358-amtech.vn/xFSTK_ZE551ML-sal358-amtech.vn/ifwi.bin size:4194468 bytes
        01:54:59 – XFSTK-STATUS–PASS
        01:54:59 – XFSTK-STATUS–Firmware download completed. Continuing to OS…
        01:55:09 – XFSTK-STATUS–Reconnecting to device – Attempt #1
        01:55:10 – XFSTK-STATUS–Reconnecting to device – Attempt #2
        01:55:11 – XFSTK-STATUS–Reconnecting to device – Attempt #3
        01:55:12 – XFSTK-STATUS–Reconnecting to device – Attempt #4
        01:55:13 – XFSTK-STATUS–Reconnecting to device – Attempt #5
        01:55:14 – XFSTK-STATUS–Reconnecting to device – Attempt #6
        01:55:27 – XFSTK-STATUS–Reconnecting to device – Attempt #19
        01:55:28 – XFSTK-STATUS–Reconnecting to device – Attempt #20
        01:55:29 – XFSTK-STATUS–Timeout to detect the device, make sure to charge up your phone before flashing

        • Waltham

          Mar 23, 2017 at 11:12 am

          Oh, by the way, it’s the same with both GP Flag Override values of 4 and 5 zeros (0x80000807 and 0x800000807).

        • Luciano

          Apr 6, 2017 at 8:38 am

          Any solution? Same issue here.

        • emrah

          Jul 17, 2017 at 8:32 pm

          do you fixed?

  3. Juan

    Jan 6, 2017 at 12:53 am

    thank you soooooooooooooooooooooooooo much…..it works!!!!

    • yzgyr

      Jan 25, 2017 at 7:41 pm

      My screen does not turn on. It vibrates when I plug in the USB cable but nothing happens when I press the power button. I tried long, short power button with and without vol + and same with vol – . Any suggestions? I also unplugged the battery (had to unscrew bat cover)


      • yzgyr

        Jan 25, 2017 at 7:42 pm

        BTW xFSTK says: No provisioning in progress

      • Bjako

        Mar 27, 2017 at 6:37 pm

        Im having exactly the Same Problem, do you have an solution for it yet?

  4. Robin

    Nov 25, 2016 at 2:55 pm

    my zenfone 2 is bricked.i tried the method given but when i connect my phone it automatically switched on but only stays in Asus Logo and after sometimes it vibrates and restart again. I tried to power off then Power on + down volume button but it seems like there is no vibrate but only the sound of detection of the cable then dropped again. and the begin download has no progress at all. please help me T.T

  5. Maku Suchinben

    Nov 17, 2016 at 1:20 pm

    I got this problem, When I connect my phone to the computer, It vibrates 2 times and Asus logo apears, and after 20-30 seconds it shuts down and turn on again and vibrates 2 times, and it keeps on looping when my phone is connected to the computer. Because of that, I cant go “Begin Download” in the program. Please help, Thank you!

    • Divyanshu

      Dec 20, 2016 at 9:51 pm

      Hey did you find any solution , I am having the same problem , plz help me ,plz ,plz plz plz !!!

      • rob

        Jan 5, 2017 at 1:05 pm

        hey guys, I had a similar problem with my ZE551ML. I went through the same frustration and pain, so if you’re still looking for a solution I could help you.

        • Alex

          Mar 22, 2017 at 11:43 am

          please i’m stuck with the same problem

  6. muwafaq

    Sep 30, 2016 at 6:54 am

    Actually i manually upgraded my zenfone 2 from lollipop 5.0 to 6.0.1, I didn’t like it that’s y I decided to downgrade it to the stock ROM using fastboot method, but when done with the steps of fastboot, I can’t get into my phone again as it just keeps showing the screen of recovery mode, restart bootloader and normal boot etc. I need your urgent help..I’m in big trouble. Regards

    • Kannan

      Sep 30, 2016 at 8:37 am

      I think you have followed a wrong method. To downgrade your Zenfone 2 to lower version, you need to flash the original recovery.img, bootloader.img, boot.img and then sideload the firmware.

      However, do a factory reset in recovery and see whether it help you.

      • Abirock

        Oct 19, 2016 at 9:34 am

        bro i cont able to flash ROM or any recovery after

        the Xfstk downloder

        all fastboot commands are geting error ?

        how solve it and help me to flash Stock ROM pls

        • Danny

          Jan 16, 2017 at 8:06 pm

          Hey bro did you find any solution , I am having the same problem i cannot do anything to my smartphone if i go to recovery boot always back to USB symbol and then Open xFSTK again and stuck in fastboot, every command in CMD has error !

  7. George

    Sep 19, 2016 at 3:46 pm

    Need the 3 files for me175cg model. would please send a link for me. Pleaseeeee!!!!

  8. Jake

    Sep 14, 2016 at 4:25 pm

    Mine restarts after it says continuing to os. And if starts the xfstk says reconnecting until it dies. 🙁

    • Jake

      Sep 14, 2016 at 4:28 pm

      18:52:50 – XFSTK-STATUS–Firmware download completed. Continuing to OS…
      18:53:00 – XFSTK-STATUS–Reconnecting to device – Attempt #1
      18:53:01 – XFSTK-STATUS–Reconnecting to device – Attempt #2
      etc… the poof! Nothing happens. Even if i reboot it, still no bootloader.

      • rtyu

        Oct 2, 2016 at 7:06 am

        GP Flag Override value 0x80000807
        instead of
        GP Flag Override value 0x800000807(wrong- as there is one more 0 remove it)

        • Jarl

          Oct 25, 2016 at 9:13 pm

          this saves me… I followed the other one, with the 5 zero’s, thank you very much

          • somebuddy

            Nov 9, 2016 at 3:24 am

            thank you so much guys !!!!!!!!!! i’ve got the same problem, there was an extra zero. It’s 0x80000807 and not 0x800000807 !!

        • KEN NG

          Jun 17, 2017 at 9:42 am

          THANKS. IT WORK.

      • Bharath Raj

        Feb 3, 2017 at 1:15 pm

        Place tell me that u have solved the problem occurred in xfstk downloder
        I too facing the same problem after attempt 20 it is disconnecting

  9. Jan Stout

    Sep 11, 2016 at 10:48 pm

    If the firmware update is stuck in a loop, check if you enabled the “Enable GP flag override”. I got out of the loop after enabling this setting.

  10. Double

    Sep 11, 2016 at 9:23 am

    hold vol+ when connecting usb to pc, works well for win 7 not sure for 8, 10… had success with this and was easier than it sounds if u follow all the steps properly. just make sure the moorefield driver is installed

  11. Shivendra

    Sep 6, 2016 at 6:40 pm

    My xFSTK is stuck in a loop.
    It says – “XFSTK-STATUS–Firmware download completed. Continuing to OS…”
    then phone restarts and it starts from the beginning again.
    Am I doing something wrong ?

    • Kannan

      Sep 7, 2016 at 7:00 am

      The method said restores bootloader, if it is broken. It will not restore OS

      • Amar

        Jan 20, 2017 at 4:47 am

        even aFter xfstk process completed . the device is not getting detected in asus flash tool. it remain stucked on the 4 color screen . how do we restore os cuz fastboot mode is unavailable .

    • Daniel Ambruzs

      Oct 28, 2016 at 3:00 pm

      Same problem here. 1 of 3 download complete then lost connection. My phone vibrate 2x and Asus logo up. Any ideas? Thanks

    • Daniel Ambruzs

      Oct 28, 2016 at 4:39 pm

      I’ve got the same problem. Any solutions? Thanks

  12. Nelson

    Sep 4, 2016 at 2:23 pm


    Please advise my problem.
    Follow all steps but after complete, message say Firmware downloaded but skip OS.
    Can anyone advise why OS is skipped?

    • Kannan

      Sep 5, 2016 at 8:36 am

      The given method restores bootloader only

      • Waltham

        Mar 23, 2017 at 11:17 am

        Hi Author. We’re not trying to get the OS restored, we’re just trying to get the message you stated in the tutorial (“Success: FW+OS download complete”) and we’re not getting it.
        Shall we skip this and go to the ASUS flash tool even if we didn’t get such confirmation? Shall we do it without the OS Image file requested in xFSTK?
        How can we proceed?

        • Kannan

          Mar 23, 2017 at 12:29 pm

          The guide is for restoring bootloader, not for OS. You need to use Asus Flash tool to restore the OS.

  13. Aakaash

    Sep 4, 2016 at 1:45 pm

    when process is completed it shows success:Download of FW completed in tool and my phone doesn’t booting up in fastmode.

  14. lucas

    Aug 22, 2016 at 3:05 am

    the xfstk not open on my windows 10 as concert?

    • Rachel

      Sep 5, 2016 at 2:25 am

      xfstk isn’t opening on my computer either (windows 10) even when I try to run as admin).

      • Paul

        Sep 28, 2016 at 4:58 pm

        Close Google Chrome & try

    • Monowar

      Aug 25, 2017 at 11:10 am

      For this, first go to settings>update and recovery>recovery>advanced start up and restart, then click on troubleshoot>start up setting advanced option then restart then press 7 to disable driver signature, after that restart and install isoc driver as administrator (it shows some warning this time, continue to install).

  15. mrrshut

    Aug 11, 2016 at 3:32 pm

    hello..i try all step…but after i click begin download…only firmware pass..but failed on OS Image…

    • Nelson

      Sep 4, 2016 at 2:19 pm

      Any success in download OS? Mine same firmware ok but OS fail.
      Any solution please advise.

      • Waltham

        Mar 23, 2017 at 11:13 am

        Same here

  16. reyzo00

    Jul 17, 2016 at 9:26 am

    hello i have a zeenfone 2 ze500 stuck in att logo please can you provide me the xfstk files to unbrick it please

  17. Moz

    Jul 12, 2016 at 10:50 am

    In very first step you say “Switch off Zenfone 2, then press Power + Vol up key together few seconds and then connect it to your computer via a USB cable.”. Now it was hard bricked how would that work? It won’t enter fastboot, I tried.

    • Kannan

      Jul 12, 2016 at 12:05 pm

      If Power + Vol up keys won’t helped, you can use fastboot command (keep in mind that Fastboot mode is for advanced Android users only)

  18. Mint

    Jun 25, 2016 at 5:55 pm

    Firmware download completed. Continue to OS

  19. mugunth

    May 25, 2016 at 1:16 pm

    when i try downloading the files to my phone it doesnt detect my device and when i long press power button the download starts but atlast says failed to download

    • Kryogen

      Aug 20, 2016 at 9:34 am

      Did you solved? I’m stuck that too

      • ankit

        Aug 22, 2016 at 4:09 pm

        stucked on same…device is not being detected

    • LucaTakehana

      Aug 26, 2016 at 5:51 am

      I whas in the same.

      1. with your phone connected to your pc,turn on your phone and dont press any button.
      2. shutdown your phone
      3. press volume down + power buttom. When the phone vibe, release the power buttom and wait your phone to be detected.

      • m3ng5k

        May 18, 2017 at 1:20 am

        Thank you. This was the missing ingredient to make the xFSTk download work.

  20. Bagindo

    May 21, 2016 at 2:23 am

    This is working good. Thank u very very much, Brother.

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