Before heading over to fix the black screen issue on your K30 / K40, make sure whether your phone is on or off.
Take your phone in a very dark environment and check the backlight. If you notice light emitting from the screen, your phone is on, else it’s off.
In case it’s off and you fail to turn it on then head over to the below post –
If your K30 turns on but the screen remains black, then check out the below troubleshooting steps –
We are going to look at all the possibilities one by one to fix this LG K40 Black screen issue –
1. Software Issue –
In case of a Black screen on your K30 / K40, you should first check if it’s a software problem. It can be a temporary software glitch caused due to a downloaded app.
a. Soft Reset
In such a case, a soft reset should fix your K40. A Soft reset is nothing but a normal restart. As the phone screen is black we cannot do a normal restart. We have to force restart the phone.


Press the Volume Down and Power Button for 10 seconds. Don’t release the buttons until the phone restarts.
If the Soft Reset fails to fix the screen, Let’s do a hard reset –
b. Hard Reset
As the screen is black we have to reset the phone via Recovery Mode. Follow the below link to reset your LG K30 / K40 via the Recovery Mode –
2. Bad Power Button
It may be that your K30/K40 is in sleep mode and you’re unable to wake it up due to the bad power button.
LG K30 Power Button
The power button on LG K30 is located on it’s back. The rear placement of the power button is a bad move by LG. After a certain period of time, it fails to register press in one go.

The power button on K40 is shifted from back to right.
If the power button fails to wake up your phone screen, use the knock-on feature. Double-tap to wake up your phone screen.
3. Soft Bricked
Is your LG K30 / K40 is stuck on a black screen after a failed firmware update? The Black Firmware Update screen is called Download Mode.
If your K30 / K40 is stuck on the above screen, we can try to restore it by flashing the stock firmware.
4. Bad LCD
In most cases, the black screen is the result of a bad LCD. If you’ve dropped your phone or it came in contact with water there are chances of LCD going bad. Many a time even a slight fall can damage the LCD.
While turning on your K30 / K40, if the phone vibrates but the screen remains black then the LCD is damaged. This indicates that the motherboard is fine but the LCD is not working.
On K40, an LED indicator also blinks while the phone is turning on.
Follow the below tutorial to fix your Broken LG K30 / K40 Screen –
LG K30 Screen Replacement Guide
5. Overheating
In some cases overheating can also result in an all-black screen. This happened with me once on my Motorola Droid Razr M. The phone was stuck on the M logo. Every phone can withstand a certain temperature above which it would cease to work.
Once the battery was all drained, the phone temperature became normal and I was able to charge & boot the phone.
6. Black Screen only during a Call
If your phone screen turns black only during a call, it’s because of the bad proximity sensor.
You can do a proximity sensor test on your K30 / K40 via the “Key Press Test” in the Hidden Menu –
Were you able to fix the Black screen on your K30/K40? Please share your outcome via the comment section below.
Soft reset worked but will go black again after a minute or two. Willsoft reset again and again. However it goes black each time after a minute or two each time. Is there anything else I can do. I have a lg k40
If the soft reset doesn’t work, try to hard reset your K40 –
https://lgk20.com/lg-k40-factory-reset-hard-reset-soft-reset-network-settings-lmx420/
I have an Lg K40, and it refuses to turn on, even though it’s fully charged
horrible help on this thing