Unlocking the bootloader on Asus ZenFone 4 is tricky. It’s simple actually, as it’s fastboot based and you don’t have to send anything to Asus to receive the unlock code over email, but it’s a bit tricky as you have to still obtain the key manually, on your PC itself, and use that to unlock the bootloader. Please note that this is the same trick for all Asus ZenFone 4 devices released in 2017, and that includes ZenFone 4 (2017), ZenFone 4 Pro and ZenFone 4 Max.

Similarly, the bootloader relock on the ZenFone 4 isn’t a single command thing. You have to get the key again, again locally (not over email), and use that within your relock command to relock the bootloader on the ZenFone 4. Let’s see how to get this done.

How to unlock and relock bootloader on ZenFone 4

We would cover the unlock and relock in two separate guides.

Get unlocked bootloader on ZenFone 4

Once again, this works on ZenFone 4 Max, ZenFone 4 Selfie and ZenFone 4 Pro too.

  1. Set up ADB and Fastboot tools on your Windows PC.
  2. Enable USB debugging on your device.
  3. Reboot your ZenFone 4 into Bootloader mode (also called fastboot mode):
    1. Power off your device. Wait for 4-5 second after screen goes off.
    2. Press and hold Power and Volume Up buttons together until you see anything on screen. That’s it.
  4. Open the command window in your PC. Hit Windows key on keyboard, and type cmd. Now click on command prompt program from the list. This will open the command window. Alternatively, in any folder on Windows Explorer, type cmd in address bar above, and hit enter key.
  5. Connect the device (in bootloader mode, from step 3 above) to PC.
  6. Let’s unlock the bootloader now.
    1. Obtain the key. Run this command for that in the command window. This will save the key into a new file called key.txt on your PC.
      echo > key.txt
    2. Unlock the bootloader. Finally!
      fastboot oem get_unlock_key key.txt
    3. Done. Your ZenFone 4 is not bootloader unlocked. Run the command below to reboot into bootloader mode again, and it shall say Unlocked now.
      fastboot reboot-bootloader
  7. That’s it. You can restart your device back to Android OS with the command below.
    fastboot reboot
  8. Now, you can install the TWRP recovery, and use the TWRP to root your ZenFone 4. It’s all do-able now, and pretty easy too.

Relock unlocked bootloader on ZenFone 4

Once again, this works on ZenFone 4 Max, ZenFone 4 Selfie and ZenFone 4 Pro too.

  1. make sure you have ADB and Fastboot set up on your PC. And USB debugging enabled.
  2. Reboot your ZenFone 4 into Bootloader mode (also called fastboot mode):
    1. Power off your device. Wait for 4-5 second after screen goes off.
    2. Press and hold Power and Volume Up buttons together until you see anything on screen. That’s it.
  3. Open the command window in your PC. Hit Windows key on keyboard, and type cmd. Now click on command prompt program from the list. This will open the command window. Alternatively, in any folder on Windows Explorer, type cmd in address bar above, and hit enter key.
  4. Connect the device (in bootloader mode, from step 3 above) to PC.
  5. Let’s relock the bootloader now.
    1. Obtain the key. Run this command for that in the command window. This will save the key into a new file called key.txt on your PC.
      echo > key.txt
    2. Input the key into device.
      fastboot oem reset_unlock_key key.txt
    3. No done yet. Few more commands before we have relocked the bootloader on ZenFone 4.
      fastboot erase config
    4. Actually, now we really relock the bootloader with the command right below.
      fastboot flashing lock
    5. Done. Your ZenFone 4 bootloader has been locked back. Run the command below to reboot into bootloader mode again, and it shall say Locked now.
      fastboot reboot-bootloader
  6. That’s it. You can restart your device back to Android OS with the command below.
    fastboot reboot
  7. In case you ever wish to unlock the bootloader, follow the guide above for that.

Let us know if you need any help with unlock and relock of ZenFone 4 bootloader.