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Error code reference

LG Microwave Error Code SE

Key Short Error

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Key Short Error — if key input is successive for more than 10 seconds, the display marks SE and converts to cancel mode.

First step from the service manual

Turn off set and restart

The complete diagnostic procedure includes additional test steps, resistance specifications, wiring diagram references, and component test points.

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What SE means on a LG microwave

The SE error code on an LG microwave stands for Key Short Error. This fault is triggered when the control panel detects a continuous key input signal lasting more than 10 seconds. Under normal operation, key presses are brief and discrete. When the microwave's control board receives an uninterrupted input signal beyond that 10-second threshold, it interprets this as an abnormal condition, displays SE on the screen, and automatically converts the unit into cancel mode to prevent unintended operation.

The most likely source of this fault is the membrane keypad or touchpad assembly. Over time, the conductive layers within the keypad can degrade, warp, or become contaminated with moisture or food debris, causing one or more key contacts to remain in a closed (shorted) state continuously. Physical damage to the keypad, such as a crack or dent in the control panel surface, can also press a key contact into a permanent closed position. In some cases, a malfunctioning control board may incorrectly interpret input signals and generate a false SE condition.

The first recommended diagnostic step is to turn the unit off and restart it. This clears the active fault and cancel mode, allowing you to determine whether the error returns immediately. If SE reappears shortly after restarting without any key being pressed, the keypad or control board requires further inspection. A sticky or physically stuck button is often identifiable by visually inspecting and firmly pressing each key to check for normal spring-back response.

Source: manufacturer service documentation.

Common causes of SE

  1. 01

    Stuck or jammed keypad button

    Wiring / connection

    Food debris, grease, or physical damage can cause one or more buttons to remain depressed, sending a continuous signal to the control board. Inspect each key for visible sticking or lack of spring-back when pressed.

  2. 02

    Deteriorated or shorted membrane keypad

    Part replacement

    The conductive layers inside the membrane keypad can degrade or short together over time, causing a key contact to register as continuously active. This typically requires keypad replacement to resolve.

  3. 03

    Moisture or contamination under the keypad

    Wiring / connection

    Liquid or grease that has seeped beneath the keypad surface can bridge key contacts and create a false continuous input signal. Cleaning the keypad surface thoroughly may resolve the issue if contamination is the only cause.

  4. 04

    Physical damage to the control panel

    Part replacement

    A dented, cracked, or warped control panel surface can apply constant pressure against one or more key contacts underneath, triggering the SE fault. Inspect the panel face for any deformation.

  5. 05

    Faulty control board

    Part replacement

    If the keypad checks out and the error persists after restart, the main control board may be misreading input signals and generating a false SE condition. Control board replacement is typically the repair in this scenario.

See the test procedure for each cause

Frequently asked questions about SE

What does SE mean on a LG microwave?
SE stands for Key Short Error on an LG microwave. It means the control board detected a continuous key input signal lasting more than 10 seconds, which is outside normal operation. When this happens, the microwave displays SE and switches into cancel mode to prevent unintended cooking. The cause is usually a stuck button, a damaged keypad, or contamination under the control panel surface.
Will resetting my LG microwave clear the SE error?
Turning the microwave off and restarting it will clear the SE display and cancel mode temporarily. However, if the underlying cause, such as a stuck key or shorted keypad, is still present, the error will return shortly after restart. A reset is useful as a first diagnostic step to see whether the fault is intermittent or persistent.
How do I fix the SE error on my LG microwave?
Start by turning the unit off and back on to clear the fault. Then inspect each button on the control panel for sticking, debris, or lack of normal spring-back response. Clean around the keypad surface to remove any grease or moisture. If the error returns immediately after restarting with no buttons pressed, the membrane keypad or control board likely needs to be replaced.
Is it safe to use my LG microwave when it shows SE?
When the SE error is active, the microwave automatically converts to cancel mode, which means it stops normal operation on its own. The unit should not be used for cooking while the error is present, as the control system may not respond predictably. Resolve the underlying keypad or control issue before returning the microwave to regular use.
How much does it cost to repair an SE error on an LG microwave?
Repair costs vary depending on the root cause. Cleaning a contaminated keypad costs little to nothing beyond your time. A replacement membrane keypad part typically runs in the range of $20 to $60 depending on the model. If the control board is the source of the problem, parts alone can range from $50 to $150 or more, with professional labor adding to that total.

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