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)


  1. even aFter xfstk process completed . the device is not getting detected in asus flash tool. it remain stucked on the 4 color screen .

  2. I follow all the instruction, after i need flash my ze550ml using asus flash tool, my phone not detected on my pc..
    Please help me, hown i can solve it

  3. Hi guys.
    I have ze551ml and i was android 6.0.1
    And my rom was “ww”
    I went to downgrade to lolli pop.
    I download the wrong firmware and placed in root of /sdcard and restart my phone.
    It says”system update found!” I click and OK that…system restarted and upgrade process started.then it start from bootloader.i select “normal boot” it’s again start from bootloader …i select that again and again…it happen the same…i choose the “recovery mod”…there is no happen again…there is no os…recovery mod…
    My boot loader is not unlock…my phone was not root…
    Please help me to recover my phone…please…
    Excuse me for my weak language…

  4. 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 ???

      • 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

    • Hi,
      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)


  5. 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

  6. 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!

  7. 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

    • 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.

      • 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

        • 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 !

    • 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.

  8. 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.

  9. 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

  10. 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 ?

      • 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 .

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

  11. Hi

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

      • 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?

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

    • 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).

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

  14. 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.

    • 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)

  15. 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


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