What's going on

Experiencing a sudden silence from your soundbar or audio receiver on the LG B4 OLED can be jarring. While this TV belongs to LG's highly acclaimed LG OLED evo design family, HDMI ARC and eARC communication issues remain one of the most frequent software-hardware headaches for home theater owners.

HDMI eARC (Enhanced Audio Return Channel) relies on precise micro-second protocol handshakes via HDMI-CEC (branded by LG as SIMPLINK). When the communication protocol desynchronizes—whether from a webOS software update, a source input change, or a minor voltage spike—the TV loses track of the soundbar, leading to muted audio or constant falling back to built-in TV speakers.

Symptoms people notice

When navigating TV hardware problems, eARC failures manifest in several distinct ways on the B4 series:

• Complete Silence: The TV indicates audio is outputting through HDMI ARC, but the soundbar produces zero sound.
• Volume Sync Without Sound: Adjusting the volume using the LG Magic Remote displays the volume bar on-screen, but the soundbar remains mute.
• Audio Drops & Stutters: Sound cuts out for a few seconds every minute or fails specifically during high-bandwidth formats like Dolby Atmos or DTS:X.
• Defaulting to Internal Speakers: The LG B4 consistently resets its Sound Out parameter to "Internal TV Speaker" every time the unit is powered back on.
• Disabled Options: The webOS menu grays out the eARC toggle button or SIMPLINK detection fails entirely.

Likely causes

Understanding why your audio setup lost communication helps isolate quick software fixes from physical hardware bugs:

1. CEC Handshake Freezes: HDMI-CEC control registers get stuck when devices enter standby mode at slightly different intervals.
2. Incorrect webOS Sound Formatting: Setting output to "PCM" or "Auto" can force compressed downmixing that your receiver cannot decode properly. "Pass Through" is required for raw bitstream audio.
3. Incompatible or Damaged HDMI Cables: Older HDMI 1.4 or 2.0 cables often lack the shielding or pin connectivity necessary for eARC data channels.
4. Wrong HDMI Port Usage: On the LG B4, only HDMI Port 2 carries the internal eARC wiring circuits.
5. Firmware Desynchronization: Out-of-sync software builds between the LG webOS system and third-party soundbar chipsets.

Quick checks first

Before pulling cables behind a wall-mounted setup, run through these essential software verifications:

• Confirm Port 2: Ensure your cable runs into HDMI 2. Ports 1, 3, and 4 do not feature ARC/eARC loopback hardware.
• Toggle SIMPLINK: Go to Settings > General > External Devices > HDMI Settings and turn SIMPLINK (HDMI-CEC) off and then back on.
• Set Digital Sound Output: Navigate to Settings > Sound > Advanced Settings > Digital Sound Output and switch the mode from Auto to Pass Through.
• Enable eARC Explicitly: In the same Advanced Settings menu, ensure the eARC Support toggle switch is switched to ON.

When it's a real hardware fault

If you have performed cold power cycles, tested multiple certified HDMI 2.1 cables, and updated all firmware without success, you may be dealing with a hardware-level failure:

• Physical HDMI Port Damage: Damaged pins inside HDMI Port 2 can prevent physical contact on the CEC control line (Pin 13) or eARC utility lines (Pins 14 and 19).
• Blown HDMI Controller/EDID Chip: Electrostatic discharge through an HDMI cable can fried the internal HDMI chip on the mainboard, preventing the TV from reading device EDID data.
• Mainboard Degradation: If other HDMI ports fail to recognize video inputs simultaneously, the LG B4 mainboard requires technical inspection or replacement.

Soft resets vs board/panel work

Most HDMI ARC issues on modern OLED displays are soft-state glitches that do not require disassembling the television. Disconnecting power to flush the system's capacitors (a cold reboot) re-initializes the CEC registers and solves the vast majority of silent soundbar issues.

However, if physical port traces or mainboard processing chips are blown, self-repair is strictly discouraged. Modern OLED mainboards contain complex surface-mount ICs and delicate ribbon connections linked directly to the panel driver board. Opening the chassis exposes you to high-voltage power supplies and risks permanent damage to the expensive OLED panel. Hardware repairs should be handled by qualified technicians covered under warranty or professional repair channels.

Next steps

Start by executing a full wall-power cycle and verifying that your audio source is running through HDMI Port 2 with a certified HDMI 2.1 cable. Adjust your webOS audio settings to Pass Through and verify that SIMPLINK is enabled.

If the issue persists across multiple external soundbars or receivers, consult our hardware reviews section for recommendations on dedicated audio extractors or explore further troubleshooting articles across our system guides.