[ZenFone 2 Q&A, Help & Troubleshooting] fanfan54:
Definitely solved :D

Solved without losing any data :D (except settings of some non-system apps)

Hello,

I found on ZenTalk (this thread : http://www.asus.com/zentalk/forum.php?mod=redirect&goto=findpost&ptid=78184&pid=392686) a working link to Latest Marshmallow sideload zip for ZE550ML OR ZE551ML. It was the right file, finally.

I sideloaded this file using adb and recovery mode, it worked PER-FECT-LY : my phone just rebooted without any problem, like before the problem. And with latest Marshmallow obviously :cool: : I immediately received messages, could access to my pictures, apps, with the same settings than before, in French (just one thing: settings for some non-system apps are reset)

Here is guide of everything I did to unbrick a Marshmallow ZE550ML stuck on USB logo with no bootloader :

(Note: I recommend you to charge your ZenFone for a few hours as soon as you'll get fastboot menu at step 1, so it will not shutdown... Even if it's not turning on the orange LED, it's charging :) )

(Note also that these are the steps I had to do in order to unbrick MY phone without losing data and installing Marshmallow. For your phone some steps might be unnecessary, if you're lucky... I know this is a very long guide but I had to do this in MY case)

1. Flash basic bootloader with xFSTK Downloader to boot fastboot

I had, first, to switch to advanced startup with support for unsigned drivers (video tutorial here),

install Asus USB drivers (link to Asus USB drivers here - note: video tutorial to install drivers from inf (repeat for every device available : ADB Interface, Bootloader Interface, etc...) )

and IntelSocUSB driver (link to IntelSocUSB driver 1.2.0 - Note: Before finishing IntelSocUSB setup it will ask you to configure a device : you'll have to connect your ZenFone 2 using an USB cable to your computer, while it's displaying USB logo, and WAIT FOR DETECTION IN Device Manager as "Moorefield device" under "Intel Soc" section),

to flash a fastboot bootloader (link to xFSTK_ZE550ML-sal358-amtech.vn for ZE550ML / link to xFSTK_ZE551ML-sal358-amtech.vn for ZE551ML) using xFSTK Downloader (link to xFSTK Downloader 1.7.0) [B

(guides for everything in this step 1: english version - same in vietnamese with screenshots and valid links - detailed PDF for xFSTK with screenshots).[/B] => phone boots on fastboot

2. Flash a lollipop ROM (or Marshmallow raw if you find it) with Asus Flash Tool to repair fastboot info (like serial number) and access recovery if you want to install Marshmallow from a zip

In order to get a working recovery menu (because I found a zip for Marshmallow but no raw, I'll have to install a recovery),

I had to install Asus Flash Tool (link to Asus Flash Tool 1.14 - Note: archive password is

www.asus-zenfone.com

),

flash a Lollipop raw (link to WW_ZE550ML_2.20.40.149.raw) on my ZenFone 2 ZE550ML using Asus Flash Tool (Model: ZE550ML - wipe data : no)

(guides for everything in this step 2: english version - same in vietnamese with screenshots and valid links)

BUT because Asus Flash Tool will wipe everything except user data and change your serial number from 0123456789ABCDEF to your legit serial number, flashing will NOT work and process will be ENDLESS because serial number has changed so phone is not found and you're not warned of that by Asus Flash Tool.

After 20 minutes of "OKAY" status displayed in green text on your phone, after 20 minutes of "a500cgfastboot.exe" running in task manager,

I think you can safely unplug USB cable, abort Asus Flash Tool by closing this software, killing "a500cgfastboot.exe",

rebooting phone (notice serial number change in fastboot info on phone's screen) and flash again with same settings but the new serial number (different of 0123456789ABCDEF).

This flash should work, after an hour or less you'll see in Asus Flash Tool that it's finished.

3. Flash Marshmallow zip with adb sideload

Finally, you'll have to shut down your phone,

boot in recovery mode (guide is here),

connect it to computer, select "apply update from adb",

install adb (link to ADB Installer 1.4.3 - Note: install it system-wide but don't install Android USB drivers) on your computer,

download zip OTA for Marshmallow (link to UL-Z008-WW-4.21.40.54-user.zip for ZE550ML / link to UL-Z00A-WW-4.21.40.61-user.zip for ZE551ML),

open a command prompt in the folder where you downloaded files (using "File > Open command prompt > Open command prompt" in the Windows Explorer's ribbon), then type :

adb devices

to verify that your phone is detected (you should see your serial number in cmd),

then type the following command to flash Marshmallow stock (zip is NOT pre-rooted if you want to root you'll have to do it after) :

ZE550ML

adb sideload UL-Z008-WW-4.21.40.54-user.zip

ZE551ML

adb sideload UL-Z00A-WW-4.21.40.61-user.zip

It may take a while decompressing then sending to phone. Then select "wipe cache partition" in your recovery menu,

wait until you see again the menu (so, wait until end of wiping cache), and select "reboot").

Now pray, and your device should magically boot the latest beautiful stock Marshmallow ROM from Asus, with all your data, exactly like before you bricked it.

It worked for me, but with the right new images it should work perfectly for you...

Enjoy this small guide, I hope you'll appreciate hard googling work :p

Thank you all, my problem is solved :)