What's going on

The LG C4 OLED is a benchmark television in the LG OLED evo lineup, but HDMI eARC/ARC communication failures remain a frequent frustration for audio enthusiast setups. HDMI eARC (Enhanced Audio Return Channel) relies on a precise hardware and software handshake between webOS and your soundbar or AV receiver. When this handshake breaks, sound suddenly reverts to internal TV speakers, cuts out intermittently, or mutes completely.

Symptoms people notice

• Silent Soundbar: TV shows eARC connected, but no sound comes through external speakers.
• Defaulting to Internal Speakers: webOS repeatedly switches audio back to Internal TV Speakers upon boot.
• Volume Control Loss: The LG Magic Remote no longer adjusts soundbar volume via SIMPLINK (HDMI-CEC).
• Intermittent Dropping: Audio cuts out every few minutes or stutters when switching apps (e.g., Netflix to YouTube).
• Audio/Video Desync: Severe lip-sync delay when passing Dolby Atmos or multichannel audio through to a receiver.
• No Power Sync: Soundbar fails to turn on or off alongside the television.

Likely causes

1. HDMI CEC (SIMPLINK) Cache Lockup: Corrupted handshake data stored in TV or soundbar volatile memory.
2. Incorrect HDMI Port Usage: Connecting the soundbar to HDMI 1, 3, or 4 instead of the designated eARC port (HDMI 2 on the C4).
3. Misconfigured Audio Settings: webOS audio output set to 'Auto' instead of 'Pass Through' causing decoding conflicts.
4. Incompatible or Damaged Cable: Using an older High-Speed cable instead of a certified 48Gbps Ultra High-Speed HDMI cable.
5. CEC Device Conflicts: Other connected HDMI devices (Apple TV, Nintendo Switch, cable boxes) interfering with HDMI-CEC signaling.
6. Main Board Controller Fault: Rare physical component failure within the TV's HDMI interface board.

Quick checks first

Before tearing down your media setup, start with simple physical and setting checks:

• Verify Port 2: Confirm your HDMI cable connects directly into HDMI 2 (eARC/ARC) on the LG C4 rear panel.
• Power Cycle Everything: Unplug the TV and soundbar power cords from the wall. Disconnect the HDMI cable. Wait 5 minutes, reconnect the HDMI cable, and plug both back in.
• Check SIMPLINK: Press Settings on your remote, go to General > Devices > External Devices > HDMI Settings, and ensure SIMPLINK (HDMI-CEC) is enabled.
• Adjust Sound Format: Navigate to Sound > Advanced Settings > Digital Sound Output and toggle it from 'Auto' to 'Pass Through'.

When it's a real hardware fault

If soft resets, new cables, and audio setting adjustments produce no results, you may be facing a physical hardware issue. Electrostatic discharge (ESD) during hot-plugging cables or power surges can damage the physical HDMI receiver IC on the LG C4 main board. Physical signs include a loose HDMI 2 port housing, hot-plug detection failure across multiple devices, or the TV completely failing to detect any device plugged into HDMI port 2 while other HDMI ports function normally.

Soft resets vs board/panel work

The vast majority of eARC issues on LG TVs are software logic jams or handshake state failures. Performing a factory reset or cold power cycle resolves most eARC dropout complaints. However, if the HDMI port itself is shorted or the main processor board has damaged audio tracing, fixing the issue requires removing the back cover and replacing the main logic board. Board replacement requires ESD safety precautions and exact part matching, making it a step beyond basic home troubleshooting.

Next steps

If you have verified your cable and settings without success, check our broader TV problems hub for general audio troubleshooting guides. You can also explore our LG OLED evo breakdown or look through our hardware reviews to determine if your soundbar or audio receiver has known firmware compatibility bugs with recent webOS builds.