The LG C5's Game Optimizer is the best gaming UI on any TV — when it works. Common failure modes: it doesn't auto-switch when the PS5 or Xbox is detected, VRR is greyed out, ALLM doesn't engage, or 4K/120Hz can't be enabled. Here's how to fix each.
Quick answer
- Game Optimizer not switching on automatically: enable HDMI Deep Color on the input port the console is plugged into
- VRR greyed out: the console's VRR setting must also be enabled, AND the HDMI cable must be Certified Ultra High Speed
- 4K/120Hz not available: enable 4K @ 120Hz in HDMI Deep Color settings; some TVs only enable this on specific HDMI ports
- ALLM not detecting console: enable HDMI-CEC (LG calls it SimpLink) and confirm the console outputs the ALLM signal
- Always: power cycle TV and console for 30 seconds with HDMI cable disconnected, then reconnect
Symptoms
- Pressing the gear button doesn't open the Game Optimizer dashboard
- Game Optimizer says "VRR: Off" even though it's enabled on PS5/Xbox
- HDR doesn't engage during gameplay (works for streaming apps)
- 4K/120Hz option is greyed out in console video settings
- Console shows "ALLM not supported" warning
- Game Mode doesn't auto-engage; TV stays in Standard or Vivid
Step 1: Enable HDMI Deep Color (the most common fix)
This is required for 4K/120Hz, VRR, and Dolby Vision Gaming on every C-series LG including C5:
- Press Settings on the magic remote
- Go to All Settings → General → Devices → HDMI Settings
- Find HDMI Deep Color
- Enable Deep Color for the specific HDMI port your console is plugged into
You must enable Deep Color per port — toggling it on HDMI 1 doesn't enable it for HDMI 2. If your PS5 is on HDMI 3, that's the port that needs Deep Color enabled.
Without Deep Color, the C5 caps that input at 4K/60Hz with 8-bit color. With Deep Color, the input runs at full 48 Gbps with 4K/120Hz, 12-bit color, VRR, and HDR all simultaneously available.
Step 2: Confirm the console settings
PlayStation 5 / PS5 Pro
- Settings → Screen and Video → Video Output
- Resolution: 2160p
- HDR: Always On (or On When Supported)
- 120 Hz Output: Automatic
- VRR: Automatic
- ALLM: Automatic
If 120 Hz Output shows "Unsupported," the TV isn't reporting 4K/120Hz capability. That's almost always the HDMI Deep Color setting from Step 1.
Xbox Series X / Series S
- Settings → General → TV & Display Options
- Resolution: 4K UHD
- Refresh Rate: 120 Hz (Series X only — Series S does not support 4K gaming)
- Video Modes: enable Allow 4K, Allow HDR10, Allow Dolby Vision, Allow Auto Low Latency Mode, and Allow Variable Refresh Rate
Step 3: Cable test
The C5 requires a Certified Ultra High Speed HDMI cable for full HDMI 2.1 features. The cable bundled with your console is usually fine. Third-party cables — even ones marketed as "HDMI 2.1" or "8K" — frequently fail at sustained 48 Gbps.
Symptoms of a failing cable:
- 4K/120Hz works for 30 seconds then drops to 60Hz
- VRR enabled but the screen tears or stutters
- Random black flashes during HDR scenes
- HDMI handshake fails when launching specific games
Replace the cable with a Certified Ultra High Speed HDMI cable. Look for the holographic certification sticker — that's the only reliable verification.
Step 4: Power cycle correctly
If settings look right but features don't engage:
- Turn off the C5 with the remote
- Turn off the console
- Unplug the HDMI cable from both ends
- Unplug the C5 from wall power for 30 seconds (not 10 seconds — the C5's power supply has capacitors that need time to discharge)
- Reconnect HDMI to the same port as before
- Plug TV back in and turn on
- Turn on console
- Wait 60 seconds for HDMI handshake to complete
This sequence resets the HDMI handshake state on both ends. Many "VRR stopped working after a firmware update" cases resolve here.
Step 5: Verify Game Optimizer auto-switching
Game Optimizer auto-switches via ALLM (Auto Low Latency Mode). The TV detects an ALLM-capable signal from the console and automatically activates Game Mode and the Game Optimizer dashboard.
If auto-switching isn't working:
- Enable SimpLink (HDMI-CEC): Settings → All Settings → General → Devices → HDMI Settings → SimpLink: ON
- Confirm the console has ALLM enabled (Step 2 covers this)
- Set the input picture mode to "Auto Mode" or "Game Optimizer": Settings → Picture → Picture Mode → for the gaming HDMI input, set the picture mode to Game Optimizer (this makes auto-switch unnecessary — it's always in Game Mode for that input)
If you have multiple gaming consoles on different inputs, set each to Game Optimizer manually rather than relying on per-input ALLM auto-switching.
Step 6: Check for firmware updates
LG releases firmware updates that fix HDMI 2.1 issues. The C5 has had multiple ALLM and VRR-related firmware patches in 2025 and 2026.
Settings → All Settings → General → System → Additional Settings → About this TV → Check for Updates
Allow automatic updates: same menu, toggle Allow Automatic Updates ON.
After updating, repeat Step 4 (full power cycle) — firmware updates frequently require an HDMI handshake reset to take effect.
Step 7: Try a different HDMI port
The C5's HDMI 2.1 ports all support full 48 Gbps, but specific ports have known firmware quirks. If HDMI 1 isn't working reliably, try HDMI 2, 3, or 4. Don't forget to enable HDMI Deep Color on the new port (Step 1).
Specific issue: HDR works for streaming, not for games
This is almost always the console's HDR setting, not the TV. Console-level HDR is separate from app-level HDR.
PS5 / PS5 Pro: Settings → Screen and Video → Video Output → HDR → Always On
Xbox Series X: Settings → General → TV & Display Options → 4K TV Details → HDR for Gaming should show "Supported"
If HDR for Gaming shows "Not Supported," the TV isn't reporting HDR capability for that input — back to the HDMI Deep Color setting.
Specific issue: Dolby Vision Gaming greyed out
Dolby Vision Gaming on PS5 was added via PlayStation firmware in late 2024 and works on the C5. Requirements:
- PS5 system software 9.00 or later
- HDMI Deep Color enabled on the PS5's port
- HDR set to Always On in PS5 video output settings
- Dolby Vision-supported game (only certain titles support DV Gaming)
For Xbox Series X, Dolby Vision Gaming has been available since 2022 and just needs Allow Dolby Vision enabled in TV & Display Options.
When none of the above works
Factory-reset the C5:
- Settings → All Settings → General → System → Reset to Initial Settings
- Re-run Quick Setup
- Re-enable HDMI Deep Color and SimpLink (Steps 1 and 5)
- Reconnect console
If a factory reset doesn't fix the issue, the HDMI port itself may have a hardware fault. LG covers HDMI port issues under the standard 1-year warranty. Contact LG support with your model number and a description of which port has the problem.
FAQ
Why does Game Optimizer dashboard show "VRR: Disabled" even after I enabled VRR on PS5? Either the cable isn't certified for full bandwidth, or HDMI Deep Color is disabled on that input port.
Can I use Game Optimizer with a soundbar passthrough? Yes, but the soundbar must support 4K/120Hz HDMI passthrough. Many soundbars cap at 4K/60Hz. If yours does, plug the console directly into the TV and use eARC to send audio to the soundbar.
Does Game Optimizer affect HDR picture quality? Game Optimizer disables some HDR processing features (Dynamic Tone Mapping) to reduce input lag. This is correct behavior — game HDR should use HGiG mode, not dynamic tone mapping. If HDR looks dim, set the console's HDR calibration carefully and ensure the C5 is in HGiG mode within Game Optimizer.
Is the LG C4's Game Optimizer different from the C5's? Functionally identical. The C5 added a slightly redesigned UI and 4K/144Hz support for PC gaming. Console gamers see no difference.