LG Washer Diagnostic Mode: How to Enter It & Read Stored Codes
LG washers offer two diagnostic doors: the service test mode (button-entered, model-specific) and Smart Diagnosis, LG's phone-based system that reads the machine through the app (or by audio tones on older models). This page explains what each does, the entry pattern LG service modes share, and how to use the results with this site's code pages.
Smart Diagnosis (the consumer door)
On equipped models: open the LG ThinQ app (or call LG support for the audio method), select Smart Diagnosis, and hold the phone near the marked point on the machine / press the indicated button combination. The machine transmits its fault data — current and recent codes plus sensor readings. It's genuinely useful: it's the same data a technician starts from, and it survives display resets.
Service test mode (the technician door)
LG service modes are entered by model-specific combinations — commonly holding two wash-option buttons (the pair varies: Rinse/Spin-side buttons on many front-loaders) while pressing Power. Once in, each press of Start/Pause steps through component tests (inlet valves hot/cold, drain pump, motor tumble/spin directions, heater where fitted) with sensor values on the display. Your model's tech sheet (inside the rear panel area or the service manual) has the exact combination and step table — use it rather than a forum's guess, because the wrong combination just starts a normal cycle.
Using what you find
Match any code the mode reports to its page here (LE, OE, IE, UE, dE families and the rest). A component that fails its service-mode step while its code never appeared on the display is an intermittent introducing itself — note the step number and behaviour.
Smart Diagnosis through the call centre, exactly as LG prints it
This is the owner diagnostic LG actually publishes for its washers, and it happens inside a phone call. Call the LG Electronics Customer Information Centre, and when the agent instructs you, place the mouthpiece of your phone close to the Smart Diagnosis icon on the appliance — LG's manuals put a maximum distance on it, about 10 mm — and press nothing else. When instructed, press and hold the button your model's manual names for the transmission (Temp. on many front-load manuals; other model families name a different button, which is why the manual for your model, not a general guide, is the authority here) for about three seconds, until the audible tones begin. Keep the phone in place until the tone transmission has finished: the display counts down the remaining transfer time, and LG's instruction is not to move the phone while the tones are being transmitted, because the data is the sound. When the countdown ends and the tones stop, resume the conversation — the agent has received the transmitted data and works from it. Two limits are printed in the manuals and worth knowing in advance: if the agent cannot get an accurate recording, you may be asked to try again (the function depends on local call quality), and Smart Diagnosis cannot be activated unless the washer turns on with the Power button — a completely dead machine is diagnosed without it, starting from the symptom.
Smart Diagnosis in the ThinQ app: the Wi-Fi route and the audible fallback
On Wi-Fi-equipped models the same feature runs through the LG ThinQ application: launch the app, select the appliance from your list of connected appliances, open the menu at the upper right of its screen, choose Smart Diagnosis and press Start Smart Diagnosis, then follow the instructions the app gives for your model. LG's manuals plan explicitly for that route failing: if the diagnosis fails several times, use the audible diagnosis method instead — select Audible Diagnosis in the app and follow the phone's instructions, holding the phone's mouthpiece to the marked point on the machine (the Smart Diagnosis logo, or the Power button on the models whose manuals say so) while the named button is held and the tones transmit. The principle to carry away is that Smart Diagnosis is one system with two transports for the same troubleshooting data: over Wi-Fi when the connection cooperates, and encoded as tones over a voice channel when it does not. A washer that 'won't do Smart Diagnosis' has usually only failed the first transport. LG's printed cautions apply to both: the feature's availability can be affected by Wi-Fi unavailability or disconnection and by app availability, and it may take a different form depending on region — none of which says anything about the health of the washer itself.
The honest position on service test mode for LG washers
Here is what this page will not give you, and why. LG publishes no universal owner entry sequence for a washer service or test mode: there is no button combination in LG's owner manuals — for front-loaders, top-loaders or combinations — that is documented as 'the' way into a component test mode, because the combinations and step tables are model-specific service information, carried in each model's tech sheet and service manual rather than in owner documentation. Any single sequence presented online as working for LG washers generally is, at best, one model's service procedure generalised past its evidence, and at worst a combination that simply starts a normal cycle, changes a setting, or enters a different mode entirely (a download-cycle or rinse-aid-style settings display is easily mistaken for a diagnostic state on LG panels). This site's dishwasher diagnostic page takes the identical position for the identical reason, and it holds here too: the owner diagnostics LG documents for its washers are Smart Diagnosis, in its call-centre, ThinQ and audible forms, plus the automatic error monitoring that displays and stores the codes themselves. If a technician runs a test mode on your machine, that is their model's service documentation at work — the step results are still worth asking about and noting, because a component that fails its service step while never showing a code on the display is an intermittent fault introducing itself, and the step number and behaviour are the record to keep.
Using a diagnosis: from transmitted data to the right code page
A Smart Diagnosis session and a displayed code answer different questions, and using them together is the actual skill. The display tells you the current headline — the code the machine is standing on now. The transmitted diagnosis gives LG's side a fuller picture, including the usage pattern the manuals mention, which is how a technician distinguishes a machine that faulted once in a flood of suds from a machine faulting weekly on a failing part. At home, your half of that work is context the transmission cannot supply: photograph the display (codes that differ by one character — dE1 from dE2, IE from its segmented rendering 1E — send whole diagnoses down wrong branches when they are misremembered), note the cycle and stage when the code appeared, and note whether the tub held water, foam or a locked door when you found it. Match the code to its page on this site for the fix path, and treat any code the diagnosis surfaces that never appeared on your display as a stored history item rather than a second emergency: deal with the live code first. If the washer will not power on at all, skip every diagnostic route — LG's own condition — and start from power: outlet, breaker, cord, then service.
Set it up before you need it
Every documented route on this page works better when it is prepared in a calm moment. Register the washer in the ThinQ app while nothing is wrong, so the appliance already sits in your connected list with its model identified when a fault makes you reach for Smart Diagnosis; the manuals' app steps assume that list exists. Photograph the model and serial label once and keep the photo with the diagnosis notes — the model is what selects the correct manual, the correct Smart Diagnosis button and the correct tech sheet, and it is never legible in the photograph you take in a hurry, mid-fault, in a dark laundry room. Download or bookmark your model's owner manual for the same reason: it is the one document that names your machine's transmission button, its code list and its reset wording, and LG's support structure assumes you can reach it. None of this is diagnosis itself, but it is the difference between a ten-minute Smart Diagnosis call and an evening of guessing — and guessing, on this subject, is how forum sequences for other people's washers end up pressed into yours.
Displays that are not faults, and will waste a diagnosis if you chase them
A diagnostic session is only as good as the report it starts from, and three LG washer displays routinely send owners into Smart Diagnosis — or into a service call — for states that are not faults at all. CL is the Control Lock function switched on: LG's manuals state that the display indicates the function is active, preventing cycle changes, and the remedy is at the panel — press and hold Control Lock for three seconds — not in any diagnostic mode. tCL is the Tub Clean alarm, which the manuals likewise state is not an error code: it means the Tub Clean cycle is running or the drum needs cleaning, and it is answered by running that cycle, not by diagnosing it. PF is a power-failure notification — the washer reporting that its supply was cut and, on many models, recalling the operation it was in the middle of; it is acknowledged with Start/Pause, and a diagnosis run on a healthy machine 'because it showed PF after the storm' will find a healthy machine. The balance family supplies the subtlest case: a lowercase-style uE display, where a model shows it, is the rebalancing attempt still in progress — the machine adding water and redistributing the load — while the capitalised UE is the same process given up as failed and paused. Diagnosing the in-progress display is diagnosing the cure. The discipline that protects every route on this page is therefore a pre-check: before any diagnosis, ask of the display in front of you whether LG's manual lists it as a state, a notification or a reminder. If it does, act on the state. Save Smart Diagnosis for the displays the manual lists as errors — those are the ones the transmitted data was built to explain.
When Smart Diagnosis itself fails
The manuals are unusually candid that the diagnosis can fail for reasons outside the appliance, and knowing the list prevents a failed session from being misread as a worse fault. On the call-centre and audible routes, transmission quality is the weak link: the function depends on local call quality, a home phone may give a better transfer than a mobile in a poor-signal room, and if the agent cannot get an accurate recording of the data you may simply be asked to try again — a retry request is a documented step, not a dismissal. On the ThinQ route, LG lists the external factors itself: Wi-Fi unavailability or disconnection, app-store policy and app unavailability can all stop the feature, and the feature may change form by region without notice. The hard limit is power: Smart Diagnosis cannot be activated unless the washer turns on with the Power button, so a dead machine exits this page entirely and goes to power checks and service. When every route fails, the fallback is not nothing — it is the displayed code itself, photographed, with the cycle, stage and tub state noted, matched to the code's page here. That is the same starting point a technician would take from the doorstep, and it loses remarkably little against a transmitted session for the common codes, whose fix paths are printed in the open.
Key takeaways
- Smart Diagnosis needs the machine powered and (for app use) the model registered — set it up before you need it.
- Exit service mode with Power; run a normal short cycle after any session to return the machine to user state.
Resetting the LG washer
LG's standard reset is a power cycle: press Power off, unplug the washer for about 5 minutes, then — with the machine still unplugged — press and hold the Start/Pause button for 5 seconds to drain residual charge from the board. Plug back in and run a test cycle. There is no hidden reset button on LG washers; any code that reappears after this procedure is an active fault the control is still detecting, not a glitch that needs a deeper reset.
Related guides
Facts on this page were checked against manufacturer documentation: www.lg.com · www.lg.com · lg.com · www.lg.com