If your LG OLED suddenly drops to a black screen or shows "No Signal," it's usually a WebOS input quirk, Deep Color handshake issue, or an HDMI cable that can't handle 4K HDR bandwidth. This guide covers LG's specific HDMI layout and the menu paths that often hide the right settings.
Quick answer
- Toggle HDMI Deep Color in Settings → General → External Devices → HDMI Input Format
- Use HDMI 2 or 4 for best 4K compatibility (eARC is on HDMI 2)
- Try a certified Ultra High Speed HDMI cable — many "no signal" issues are marginal cables
- Power on in order: TV first, then receiver, then source device
- Set conservative resolution first (4K 60Hz), then step up to 120Hz or VRR
Symptoms
- Black screen with "No Signal" message on specific HDMI ports
- Picture drops out when switching to 4K HDR or high frame rates
- Intermittent signal loss during streaming or gaming
- Device works fine on other TVs but fails on LG OLED
- Connection only works when HDMI Deep Color is disabled
Quick checks
- Confirm the correct input — Open Quick Settings input list and verify the device name matches the active port (LG sometimes renames inputs when you change icons)
- Inspect the HDMI cable — Look for sharp bends, kinks, or loose connectors. Reseat both ends until they click
- Test another source — Try a known-working device like a streaming stick in the same port
- Restart everything — Power off TV, source device, and any receiver. Unplug for 30 seconds before turning back on
Step-by-step fix
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Start with a direct connection — If using a receiver or soundbar, temporarily connect the source straight to the TV with a short HDMI cable
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Choose the right port — On 2020-2024 LG OLEDs, use HDMI 2 (eARC) or HDMI 4 for best 4K compatibility. All four ports support 4K120 on newer models
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Enable HDMI Deep Color — Go to Settings → General → External Devices → HDMI Input Format and set the active port to "Enhanced" or "4K"
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Toggle Deep Color off and back on — This refreshes stuck HDMI handshakes that cause signal drops
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Set conservative resolution first — Configure your source device to 4K at 60Hz initially. Avoid HDR or high frame rates until you get a stable picture
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Power on in clean order — Let WebOS boot to home screen, then turn on receiver (if used), then finally the source device
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Step up to full resolution — Once stable at 4K60, gradually enable 120Hz, VRR, or HDR features one at a time
If it still isn't working
Try a different HDMI cable — A surprising number of "no signal" problems are marginal cables that fail only at 4K or higher frame rates. Use a certified Ultra High Speed HDMI cable.
Identify the problem component:
- Source device issue — TV shows "No Signal" on all ports but other devices work fine
- TV issue — Multiple inputs lose signal intermittently across all devices (check for firmware updates or factory reset)
- Receiver issue — Problems only occur with receiver in chain (review receiver's 4K/8K passthrough settings)
Document what works — Create a matrix of which source/port/cable combinations succeed or fail. This helps with manufacturer support and warranty claims.
FAQ
Q: Why does my Apple TV work on HDMI 2 but not HDMI 1? A: HDMI 2 carries eARC and often has better 4K compatibility. Try toggling HDMI Deep Color for HDMI 1, or set the Apple TV to 4K SDR with Match Range/Frame Rate enabled first.
Q: The cable worked fine before — why would I need a new one? A: HDMI cables can degrade over time, and 4K HDR requires much more bandwidth than 1080p. A cable that handled basic signals may fail at 48 Gbps data rates.
Q: Should I always use "Enhanced" HDMI format? A: Yes, for 4K sources. The "Enhanced" setting enables full HDMI 2.1 bandwidth. Only use "Standard" for older 1080p devices that have compatibility issues.
Q: What if factory reset doesn't help? A: Document your testing results and contact LG support. Persistent issues after cable swaps and settings changes often indicate a failing HDMI port that needs warranty repair.
For brand-agnostic HDMI troubleshooting, see our full guide at /4k-tv-receiver-hdmi-no-signal-checklist.