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LG CO

LG Refrigerator Error CO: Communication Error — Main Board to Sub Board

Clear meaning, realistic next steps, and safe guidance without turning the page into a long repair manual.

What it means

The main control board and one or more sub-boards (such as the display board or inverter board) cannot communicate. The refrigerator's internal electronics have lost contact with each other.

Severity

High - stop using the LG refrigerator until the cause is understood or professional help is arranged.

Can you fix it yourself?

No — call a technician

Most likely cause

Main control board failure — the board is not transmitting communication signals

Estimated time for safe first checks: Professional service required.

Step-by-Step DIY Fix Guide

  1. SAFETY: Unplug the refrigerator.
  2. Reset by unplugging for 5 minutes, then restore power and check if CO clears.
  3. If CO returns, call an LG-authorized technician — internal board communication faults require specialist diagnostic tools.

If the code comes back

  • CO persists after a 5-minute power reset

What This Error Means

Error CO on your LG refrigerator means: The main control board and one or more sub-boards (such as the display board or inverter board) cannot communicate. The refrigerator's internal electronics have lost contact with each other. The refrigerator's self-diagnostic system has detected this condition.

The most frequent cause is main control board failure — the board is not transmitting communication signals. Work through the causes and fix steps below in order — many LG refrigerator errors are resolved without a service call.

LG's official guidance classifies CO as a technician-only fault. A 5-minute power reset is the only DIY step — if the code returns, contact LG Support at 1-800-243-0000.

Communication and flow faults require professional diagnosis. A power reset resolves transient electronic glitches. If the code returns after a reset, a physical component has failed.

Most Likely Cause by Symptom

The LG refrigerator may stop, pause, or refuse to complete the cycle normally.

Likely cause: Main control board failure — the board is not transmitting communication signals

Check first: SAFETY: Unplug the refrigerator.

The warning may return immediately because the appliance is detecting an internal fault.

Likely cause: Wiring harness fault — connector is loose, corroded, or a wire is broken in the communication circuit

Check first: Reset by unplugging for 5 minutes, then restore power and check if CO clears.

Common Causes

  • Main control board failure — the board is not transmitting communication signals
  • Wiring harness fault — connector is loose, corroded, or a wire is broken in the communication circuit
  • Display board failure — the sub-board is not responding to the main board
  • Power surge corrupting board communication

What Not to Do

  • Do not attempt to re-seat board connectors yourself without confirming which harness is at fault — disturbing other connections can introduce new faults

Model and Display Variation Notes

Model-family notes

  • LG refrigerator display wording and code formats can vary by series.
  • If your model behaves differently, check the owner manual before trying any deeper maintenance step.

Display and panel differences

  • Panel wording can vary by series, so confirm the exact code pattern before buying parts.

Parts, Tools and Service Options

Service option

LG service visit if the warning returns after the basic checks are complete.

Manual and model check

Check your exact model and manual before ordering any LG refrigerator parts.

Common parts

  • Main control board if board has failed ($100–$250)
  • Display/sub control board if sub-board has failed ($60–$150)
  • Wiring harness if connector or wiring fault is confirmed ($20–$60)

This section stays service-first because the page points more strongly toward support or professional repair than a routine parts purchase.

When Not to Keep Troubleshooting

CO persists after a 5-minute power reset

How to Prevent It Recurring

  • Use a surge protector on the refrigerator outlet — voltage spikes from power outages are a leading cause of control board communication faults

Related Error Codes

Extra notes

  • This page is based on LG support material and stays conservative where model-specific guidance may vary.
  • The goal is to help you identify safe first checks before you move into parts, service, or model-specific manual lookup.

Source and model notes

Last reviewed: 2026-04-08

Based on: Based on LG support material and edited into consumer-safe guidance for the exact code family on this page.

View LG US Official Support

Model coverage note: LG refrigerator code meanings can vary by series, control panel, and model family, so use this page as a safe starting point rather than a replacement for the model-specific manual.

Important: FixThisError is an independent guide, not the manufacturer. Use your model-specific manual when the panel wording or behavior differs.

Always disconnect power before inspecting appliances. If unsure, contact a licensed appliance technician.