[ZenFone 2 Q&A, Help & Troubleshooting] laidick:
To rescue your phone from boot loop / bad /corrupted flash

Hi, i just want to share my experience on how to fix the boot loop / bad flash.

This is a great lesson learnt for my self as I did something silly to my phone.

Let me first show how&why I get my phone into boot loop .... (you may skip to the last paragraph for the tips)

A) Basically I had the below condition, and everything was working fine.

1) installed pre-rooted img ( WW_2.15.40.10 )

2) updated su binary

3) installed busybox

4) installed any system apps such as 'better battery stats'

5) frozen any system apps using titanium

(these are all I will be doing when I need to flash a new rom every time, as this is helps me to fully restore the same environment moving from one phone to another :))

B) Then I saw the new firmware released ( WW_2.15.40.13 ) via OTA.

1) I downloaded the OTA and update directly using the OTA

2) It went into recovery, during installing the new update, it prompted an ERROR dialog.

3) waited for a while (1-2minutes) doing nothing, it reboot automatically back to my previous rom

(in this stage, you will be fine, as you are still with your working rom)

C) Then I found the full firmware version from official asus and updated using this file:

1) I downloaded firmware from asus website here

2) I put the file in my INTERNAL SDCARD

3) My phone detected an update and I reboot my phone as requested.

4) It went into recovery, show 'Installing system update ...". But the progress bar hang in about 30% doing nothing (for about 2-3 minutes)

5) I tried to reboot my phone using 'power + volume up'

6) **** magic happen here, may be I pressed the button in wrong order **** It shown the recovery console output, sasying "Updating IFWI ..."

7) it still hang, then I reboot again using 'power + volume up' to fastboot mode, and selected 'NORMAL BOOT'

8) the phone was not able to boot normally, it turned into recovery and tried to flash the same update again. then I repeated step 5)-7) a few times....

D) up to now, I thought my phone is in boot loop (but actually it is NOT), and the root cause is because i have the update zip file in internal sd card. Then I did

1) re-flashed all files from pre-rooted.img (WW_2.15.40.10), and reboot, but it didn't help.

2) fastboot erase cache (PLEASE DONT DO THIS, i am just telling you what i did wrong :crying: )

3) fastboot erase userdata (same as above)

4) reboot my phone

5) It went into recovery, it prompted 'ERROR' quickly after 'Installing system update ....'

6) I tried to reboot my phone using 'power + volume up'

7) I repeated step 4)-6) a few times ....

8) **** magic happen here again, after i press power + volume up button **** It shown the recovery console output with option to wipe data/ adb sideload etc...

E) up to now, the only thing I could do is 'adb sideload', then

1) I selected adb sideload

2) in my PC, I run 'adb sideload UL-Z00A-WW-2.15.40.13-user.zip'

3) In recovery console, it shown the installation progress, and similar to C6), it hangs in 'Updating IFWI...'

4) However, in my PC the adb sideload console, the % progress was still updating. I waited until it reached 100% (it took about ~15 minutes)

5) My phone finally rebooted back to the ROM, but it was in empty state (factory reset). I need to re-configure everything of my phone.

F) up to now... my phone basically back to a workable state. but i still want root ... (yes i was crazy at that time still trying to kill my phone)

1) I downloaded the pre-rooted.img (WW_2.15.40.13), and flashed everything using fastboot

2) all working fine.

Now. I get my phone in clean state, I just need to reinstall/reconfigure everything, and of course run my A1)-A5) to get my environment back.

It took my 2 hours to fix everything ... tired.

Finally, this is my quick summary... you may want to pay attention to when you are flashing any update.

1) You should never flash any OTA update if you have modified any system files. - Don't do B) if you did A)

2) You should be patient enough to wait when flashing the official firmware full image. It does take more than 15 minutes doing nothing on the screen. - Don'd do C5) to C8)

3) You should never erase cache/userdata unless you know what exactly does this mean. - Don't do D2) - D3)

4) You can flash the pre-rooted.img any time if you want to upgrade to latest version. You just need to re-modify your system files if you like. A1)-A5)

5) There is a magic button combination in recovery I am sure. However, I am not able to reproduce it consistently. As it only works when you see the 'ERROR' screen. If anyone knows what happened in C6) & D8). Please let me know....

It's a bit long... thanks for reading. Hope it helps. :angel: