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A vertical line that remains on your LG TV can come from a loose cable, an incompatible external device, an incorrect picture setting, an OLED uniformity issue, or a television fault. The fastest way to separate those causes is LG’s built-in Picture Test (called Screen Self-Diagnosis on newer webOS versions): if the line is absent from the test image, investigate the source, cable, or input; if it appears in the test image, the TV itself may need inspection.
Work through the checks below in order. They start with reversible causes and end with the evidence you need for LG support or an authorized service provider.
What a vertical line on an LG TV usually means
A stripe may be green, white, black, or another color, and it may run from the top to the bottom of the screen or appear only along an edge. Color and position alone do not identify the failed component. The decisive question is whether the line is generated by the TV panel or by the signal reaching it.
LG’s own decision rule is simple: if lines or dots also appear in the internal test image, the TV may need inspection. If the test image is clean, the panel is less likely to be the source; concentrate on the connected device, broadcast signal, input, or cable instead.
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Do not start by buying a replacement panel or repeatedly running maintenance routines. A disciplined isolation sequence prevents you from paying for a panel repair when the actual fault is a damaged HDMI lead or an incompatible device.
First check: run LG’s internal Picture Test
The test displays imagery generated by the television rather than by a set-top box, console, streaming player, or antenna signal. Use the menu path that matches your webOS generation:
| TV software generation | Menu path | What the result tells you |
|---|---|---|
| webOS 6.0 and later (generally 2021 and newer) | Settings > All Settings > Support > Screen Self-Diagnosis | A line in the generated test image points toward a TV-side fault; a clean image points toward the source chain. |
| webOS 5.0 (2020 models) | Settings > All Settings > Support > Additional Settings > Picture Test | Use the same source-versus-TV decision rule. |
| webOS 4.5 and earlier | Settings > All Settings > Picture > Picture Test | Use the same source-versus-TV decision rule. |
If the line appears in the test image
Photograph the test screen and note whether the line is continuous, intermittent, or accompanied by other dots or bands. Because the image is produced by the TV, a persistent line here is not explained by your console, set-top box, streaming service, or HDMI cable. Continue with the basic checks below, then treat the result as a service-inspection case if it remains.
If the test image is clean
Return to the LG home screen and look for the line there. Then test a second input or source. A line visible only while one device is selected is more likely to involve that device, its signal, or the cable feeding that input. A clean home screen and clean test image strongly shift the investigation away from the panel.
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Isolate HDMI, antenna, and external equipment
Loose or damaged HDMI and antenna connections can create lines and other visual noise. Perform this isolation with the TV turned off so that you can inspect every connection safely.
- Turn the TV off. Disconnect every antenna and HDMI lead, including cables attached to receivers, consoles, computers, and streaming devices.
- Inspect both ends. Look for bent, loose, or visibly damaged connectors and for debris or damage around the TV’s ports. A connector that does not seat firmly is a diagnostic suspect.
- Reconnect one path at a time. Push the cable fully into the TV and the external device, then power on and check the picture.
- Try another input. Move the same device to a different HDMI input when practical. If the line follows the device, the device or its output settings deserve attention; if it stays with one port, record that pattern for service.
- Test a spare cable. A high-speed HDMI cable is a reasonable diagnostic replacement. It can prove that the original lead is at fault, but it cannot repair a line that also appears in the TV’s own test image.
- Reconnect the antenna last. If the line returns only with broadcast reception, compare another channel or source and record the difference. That points toward the incoming signal path rather than the display panel.
After each change, check the LG home screen and the affected input. Changing several cables and devices at once makes it impossible to tell which action changed the symptom.
Correct the aspect ratio before deeper troubleshooting
An incorrect aspect-ratio setting can draw lines along the screen edges. Open the TV’s Aspect Ratio control in Picture settings and test 16:9, then Original if the source is intended to preserve its native shape. Watch the same content after each change.
This check is most relevant when the line is confined to an edge, changes with different programs, or disappears when you switch between the home screen and a source. If a fixed stripe remains in the same position on every screen, aspect ratio is less likely to be the cause, but the setting is quick to rule out.
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Check HDMI Deep Color when only one input is affected
LG associates HDMI Deep Color incompatibility with lines, flicker, and color distortion. If the symptom occurs on only one HDMI input, open that input’s HDMI settings and turn HDMI Deep Color off for the affected connection. Retest the same device and content.
Do not change the setting on every input unnecessarily. The relevant test is whether disabling it on the incompatible device’s input removes the line while other inputs remain unchanged. If the line persists with Deep Color off and also appears in Picture Test, restore the setting that matches your device and move on to service preparation.
OLED-only step: run Pixel Cleaning when appropriate
OLED televisions have a maintenance routine intended to address panel-uniformity and image-retention-type problems. LG labels it Pixel Cleaning in current OLED Care or OLED Panel Care menus; some older webOS versions call the function Pixel Refresher.
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Pixel Cleaning is not evidence that software can repair a mechanically damaged or failed panel. If the vertical line remains in the generated test image, remains across channels and inputs, or is unchanged after the routine, treat it as a hardware inspection issue. LCD, LED, and QNED models do not use this OLED-specific maintenance step.
Use the symptom pattern to choose the next action
| What you observe | Most useful interpretation | Next action |
|---|---|---|
| Line appears in Picture Test and on the home screen | The TV itself may have a panel or internal display fault. | Complete cable and setting checks, document the result, then contact LG support or an authorized service provider. |
| Picture Test is clean; line appears on one HDMI input only | The connected device, HDMI lead, input compatibility, or that port is implicated. | Reseat connections, test a spare high-speed HDMI cable, try another input, and disable HDMI Deep Color for that input if the device may be incompatible. |
| Picture Test and home screen are clean; line appears with antenna reception | The broadcast or antenna path is more likely than the panel. | Reseat the antenna lead and compare another channel or source. |
| Line is confined to the screen edge and changes with framing | Aspect-ratio processing may be drawing the edge line. | Test 16:9 and Original in the Aspect Ratio control. |
| OLED line or stain appears in test imagery and survives external-device checks | Pixel Cleaning may be worth one maintenance cycle, but persistence points toward inspection. | Run Pixel Cleaning (Pixel Refresher on some older models), then document whether the symptom changed. |
| Line disappears when a cable or device is replaced | The replaced item was part of the signal fault. | Keep the known-good cable or device and monitor the TV’s own test image for recurrence. |
The same comparison can be made across display types:
| Display type | Relevant maintenance check | What a persistent test-image line means |
|---|---|---|
| OLED | Pixel Cleaning or Pixel Refresher after Picture Test and connection checks | Further maintenance is unlikely to substitute for inspection if the line remains. |
| LCD, LED, or QNED | No OLED Pixel Cleaning step; concentrate on test image, cables, inputs, and settings | A line in the test image is a TV-side inspection case. |
When a vertical line requires service
Contact LG support or an authorized service provider when the line remains in Picture Test after you have reseated cables, tested another cable or input, checked Aspect Ratio, and completed the appropriate OLED maintenance. LG’s published guidance does not provide a universal repair price, repair-time promise, or success-rate statistic for this symptom, so an inspection is necessary before anyone can give a reliable estimate.
Before contacting support, collect the information that lets the technician reproduce the fault:
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- TV model number and serial number.
- Purchase date and proof of purchase if available.
- A full-screen photograph showing the line, plus a photograph of the Picture Test result.
- The webOS generation or software information shown by the TV.
- Whether the line appears on the home screen, every input, antenna channels, and the internal test image.
- Whether reseating or replacing an HDMI/antenna cable, changing Aspect Ratio, disabling HDMI Deep Color, or running Pixel Cleaning changed the symptom.
Ask about warranty coverage and the expected authorization process before approving a panel replacement. Coverage and service availability vary by country, model, and purchase circumstances; the cited LG support pages do not establish a single worldwide policy.
What not to conclude from a colored stripe
A green, white, or black line is not automatically an HDMI failure
Color does not tell you whether the source, cable, settings, or panel is responsible. Use Picture Test and input isolation rather than diagnosing from color alone.
A clean test image does not prove the panel is perfect under every condition
It does, however, make an external source or connection the more useful place to investigate first. Repeat the check on the home screen and another input so that a device-specific fault is not mistaken for a panel fault.
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Its purpose is OLED uniformity and image-retention-type behavior. A line that is mechanically caused or present in the TV-generated test image may remain unchanged.
A replacement cable is a test, not a guarantee
A spare high-speed HDMI cable can eliminate one common cause. It cannot correct a defect that appears with every source and in the internal test image.
LG’s published guidance and its limits
LG USA Support’s general line-troubleshooting guidance, published September 21, 2026, states: “If the lines or dots also appear in the test image, your TV may need to be inspected.” LG’s OLED vertical-lines guidance was published July 9, 2025, and its Pixel Cleaning guidance was published August 18, 2026. These pages explain the diagnostic sequence but do not publish a universal repair cost, success rate, or prevalence figure for vertical-line failures.
That absence matters when evaluating online claims. A forum post or repair quote from another model or country cannot establish what your panel will cost or whether replacement will succeed. The test result, warranty status, and an authorized inspection are the evidence specific to your television.
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A complete troubleshooting sequence
- Run Picture Test or Screen Self-Diagnosis using the path for your webOS version.
- If the test is clean, check the LG home screen and a second input.
- Turn the TV off, disconnect and inspect HDMI and antenna connections, then reconnect firmly.
- Try a spare high-speed HDMI cable and, where possible, another HDMI input.
- Set Aspect Ratio to 16:9 or Original and retest.
- If one HDMI input is affected, disable HDMI Deep Color for that input when the connected device may be incompatible.
- If the TV is OLED, run Pixel Cleaning (or Pixel Refresher on older webOS) after the preceding checks and leave the TV plugged in if the routine is scheduled after power-off.
- If the line still appears in the TV-generated image, photograph the result and contact LG support or an authorized service provider with your model, serial number, purchase date, and symptom history.
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