Root LG K40 LM-X420 / Bootloader Unlock & TWRP

LG K40 can be rooted after unlocking the bootloader and flashing a custom recovery such as TWRP. Using the custom recovery we can install a flashable Magisk or SuperSU zip file to root the device.

I’m trying to root my LG K40 MetroPCS with model number LM-X420MM. There are different variants of K40 based on different carriers. The other K40 variants are T-Mobile lmx420tm, AT&T lmx420as, factory unlocked lmx420qn, US Cellular lmx420qm & Spectrum Mobile lmx420qn.

Let’s start the procedure by unlocking the bootloader.

LG K40 Bootloader Unlocking – LMX420MM

To unlock the LG K40 bootloader we need to do the following steps –

1. Turn on the “Developer Options”

“Developer Options” is hidden by default but can be enabled quite easily. Follow this post to enable it on your K40 – LG K40 Developer Options.

2. Enable USB Debugging

After doing the first step, Go to Developer Options and enable USB Debugging.

lg k30 root

3. Connect K40 to PC via USB Data Cable

Now we are ready to connect our phone to the PC via USB data cable.

lg k30 lge mobile adb interface driver

Wait for the LGE Mobile ADB interface driver to install, after connecting the phone.

4. Use Minimal ADB & Fastboot Tool for Bootloader Unlocking

Read moreRoot LG K40 LM-X420 / Bootloader Unlock & TWRP

LG K30 Screen Replacement Guide – lmx410mk, lm-x410asr, lmx410pm

LG K30 has a curved edged 2.5D glass display with no Gorilla Glass or Panda King Screen Protection. A curved edge screen is more prone to damage than a flat one. So, it’s better to use K30 with a screen protector and case.

However, if your K30 glass or LCD is already damaged then the only solution is the screen replacement. A phone screen is made up of 3 parts. The outer glass, touchscreen digitizer and the inner LCD.

Now in most of the cases, the glass breaks but the touchscreen does work. In this case, the outer glass can be replaced with a newer one. If the impact is severe, then the digitizer and/or LCD would break. In such a case we need to change the LCD which includes the digitizer as well.

There is one more option which is the easiest one and can be done by a non-professional at home. The last option is to get an LG K30 LCD with Frame. Let’s check out these 3 methods of LG K30 screen replacement.

Follow the detailed guide to replace your broken K30 glass with a new one –

LG K30 Screen Replacement Guide / Kit / Cost – lmx410mk, lmx410as, lmx410asr, lmx410tk, lmx410(fg), lmx410cs lmx410um & lmx410ulml


1. LG K30 Glass Replacement – Outer Glass Lens without Touchscreen Digitizer

LG K30 Screen Replacement

In more than 90% of the cases, only outer glass breaks and touchscreen digitizer remains intact. In such a case, you would like to save money by replacing the outer glass only. It sounds great but is quite difficult to implement.

This new glass can be replaced only after removing the broken glass using a heat gun. The LCD film is quite thin and may get damaged while removing the broken glass.

To do this job you would need to hire a professional and you may end up spending more than the cost of LCD. Moreover, it can never match the precision of the factory fitted glass.

However, if you wish to give it a try, you can get the LG K30 glass lens for around $10.

2. LG K30 LCD Replacement

Read moreLG K30 Screen Replacement Guide – lmx410mk, lm-x410asr, lmx410pm

LG K40 Developer Options & USB Debugging- How to Turn on LMX420

“Developer Options” is found in “Settings” on LG K40 but its kept hidden by default. The options in this menu are useful for developers. It has got an extensive list of options that can do some harm if misused. That’s why its kept hidden.

However, it’s very easy to enable. Without the Developer Options, we cannot turn on USB Debugging to connect out K40 in ADB / Fastboot Mode. For writing, ADB commands the phone should be connected to the PC with USB Debugging in the enabled state.

In this post, we are going to learn, How to enable Developer Options and USB Debugging with the help of the below video and screenshots –

How to turn on Developer Options & USB Debugging on LG K40

lg k40 developer options

On your LG K40 Home Screen, swipe right and you would see the “Settings” icon. Tap on it to open.

In Settings, select the “General” tab and scroll down to the bottom of the page.

Choose the 2nd last option i.e. “About Phone”.

On the About Phone page, tap “Software Info” as shown above.

Read moreLG K40 Developer Options & USB Debugging- How to Turn on LMX420