LG Washer Diagnostic Mode: How to Enter and Read Results

Quick Answer

Enter LG Washer diagnostic mode to read stored fault codes and run individual component tests. See the entry sequence below. Diagnostic mode stores recent error events so you can find intermittent faults that clear between uses.

LG washers have two diagnostic systems. The first is the built-in service mode (entered via button sequence) that runs individual component tests - motor, inlet valve, drain pump, drum sensor. The second is ThinQ Smart Diagnosis (Wi-Fi or audio tone), which sends diagnostic data to the LG app and returns a plain-language result. Use Smart Diagnosis first if your washer supports it. Use service mode for hands-on component testing.

LgWasherSeverity: lowDifficulty: advanced75% DIY Success

Time to Fix

10–45 min

Difficulty

advanced

Parts Cost

—

Tools Needed

LG ThinQ app (for Smart Diagnosis), Multimeter (for component testing after diagnosis)

What Does the DIAG Code Mean?

LG service diagnostic mode is a firmware-level test menu that technicians use to test each component individually without running a full cycle. You can activate the motor, open the inlet valve, run the drain pump, and read sensor values independently. This lets you confirm exactly which component is causing an error code before buying parts.

Most Likely Causes

Based on aggregated repair data, here is the probability breakdown for this error code:

Need to confirm which component is causing a specific error code before buying parts40%

Intermittent error that does not reproduce during normal cycles36%

Technician service visit requiring component-level verification24%

Symptoms You May Notice

Error code appearing that needs component-level confirmation
Washer behaving abnormally but no error code displayed
Pre-repair verification before purchasing replacement parts

Tools Required for Diagnosis

LG ThinQ app (for Smart Diagnosis)Multimeter (for component testing after diagnosis)Phone or tablet with camera (to record test sequences)

Diagnostic Checklist

Follow these steps in order. We start with the easiest external fixes before opening up the machine.

ThinQ Smart Diagnosis (easiest, Wi-Fi models)

Open the LG ThinQ app on your Android or iOS phone. Select your washer from the device list. Tap Smart Diagnosis. Follow the app prompts - you will hold your phone's microphone near the washer's control panel. The washer emits a series of tones that the app decodes. The app returns a diagnosis in plain language with recommended actions. This method works even without entering the service menu and does not require opening the washer.

Enter service diagnostic mode - WM series (front-load)

Enter service diagnostic mode - WT series (top-load)

Run individual component tests

Exit diagnostic mode

Frequently Asked Questions

How do I put my LG washer in diagnostic mode?

On WM series front-loaders: hold Start/Pause and Temp simultaneously, then press Power while holding both. On WT series top-loaders: hold Temp and Rinse for 3 seconds. The display changes to show a test code. Exact button combos vary slightly by model year - if the first combo does not work, try holding the two buttons you see with lock or diagnostic icons printed above them.

What is the button sequence for LG washer diagnostic mode?

The most common sequence for WM series: hold Start/Pause + Temp, then press Power. For WT series: hold Wash Temp + Spin Speed for 3 seconds. For older WM models (WM1333, WM2455): hold the last two cycle buttons while pressing Power.

Can I run diagnostic mode without the ThinQ app?

Yes. The built-in service mode (button sequence entry) works on all LG washers regardless of Wi-Fi capability. ThinQ Smart Diagnosis is the easier option if your model supports it, but it is not required. The built-in service mode gives more control over individual component tests.

Is diagnostic mode safe to use?

Yes, with precautions. Diagnostic mode activates components on command. Run tests with the washer panels in place and keep hands away from the drum and motor. The valve tests will add water - make sure the drain hose is properly installed before running fill tests. Do not run heater tests with an empty drum.

Related Lg Washer Error Codes

Code: HUBLG Washer Error Codes: Full List Code: RESETHow to Reset an LG Washer (includes factory reset via diagnostic mode)

Same Fix Works on These Brands

Lg shares the same hardware platform with these brands. The diagnosis and repair steps are identical.

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Models Known to Experience DIAG Errors

This repair applies to most Lg washers with this error code. Common model numbers include:

WM3700HWA, WM4000HWA, WM5000HVA, WM3900HBA, WT7300CW, WT7800CW, WM6998HBA, WM8100HVA, WM3470HWA, WT7410CW

Last verified for technical accuracy on March 13, 2026