LG K40 Hidden Menu Codes – LM-X420MM, LMX420AS, LMX420TM & LMX420QN

LG K40 comes in 4 different variants. It’s available for MetroPCS, T-Mobile & AT&T. The 4th one is the Factory Unlocked Version.

There are 2 different Hidden Menus available for the MetroPCS/T-Mobile variant. The rest of the K40 variants have a single Hidden Menu. In this post, we’re going to unhide the Secret Menus and explore them in great detail as per the video and screenshots below –

LG K40 Hidden Menu Codes – MetroPCS lmx420mm / AT&T lmx420AS / T-Mobile lmx420tm / Factory Unlocked lmx420qn

lg k40 hidden menu device test

The first Hidden Menu code is common for all the K40 variants and this is the Main Hidden Menu with lots of troubleshooting options in the form of Device Tests.

To get access to this Hidden Menu open your K40 phone dialer and dial *#546368#*420#

The 4 options in the Hidden Menu can be seen in the above screenshot. They are “Device Test”, “ORT Test”, “SVC Menu” & “Field Test”. Let’s explore them one by one using the below screenshots –

1.  Device Test – LG K40 Hidden Menu

Go to “Device Test” < “SAAT” < “Service Menu – Manual Test” to view the list of Tests.

a. Auto Detecting Item Test

LG K40 auto detecting item test

The first test in the list is “Auto Detecting Item Test”. Select it to start the test.

To PASS this test you should have a SIM Card and Micro SD card in their respective slots.

In case, the memory card or SIM card is not in the slot, you can skip this test only by pressing the power & volume keys together.

b. Key Press & Proximity Sensor Test

lg k40 hidden menu key press test

This test covers the hardware keys and proximity sensor.

Press each hard key such as Power Key, Volume UP, Volume Down & Google Assistant Key.

The “ETC” option in the last screenshot above represents the Google Assistant Key.

The Proximity Sensor can be tested by blocking and unblocking the sensor as per the instructions on the screen.

The proximity sensor is located above the screen.

c. Display Check Test

lg k40 display check test

This is an LCD test that can help in identifying dead pixels if any.

The screen turns all-black then all-while under this test as shown above.

d. Ring Test

lg k40 speaker not working - ring test

Speaker issues are quite common and this test can help in troubleshooting your LG K40 loudspeaker.

Under this test, the phone rings at the maximum volume even when it’s in the “silent” or “do not disturb” mode.

e. Vibrator Test

lg k40 no vibration - vibrator test

Similar to Ring Test, in this test the phone vibrates at maximum intensity. If it fails you need to replace the vibrator motor on your K40.

f. Motion Sensor Test

lg k40 motion sensor test lmx420

We’ve already tested the Proximity Sensor. In the Motion Sensor Test, we are going to test the rest of the LG K40 sensors which are Magnetometer, Accelerometer & Gyroscope.

To perform this test, Place your K40 on a Flat Surface.

lg k40 gyroscope test

Now, stand the phone vertically and finally horizontally to clear this test.

g. Loopback Test

lg k40 audio loopback test

The next test on our list is the Loopback Test.

As the name suggests, this is a loopback between the audio from earphones and the loudspeaker.


loopback test k40 hidden menu

When one is turned on the other turns off automatically.

h. GPS, Bluetooth & Wifi Test

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1 thought on “LG K40 Hidden Menu Codes – LM-X420MM, LMX420AS, LMX420TM & LMX420QN

  1. Great article the onky one that actually was effective in helping me open uo secret menu and descriptivevas well. Well done thank u

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