FixByModel
Er CO

LG Er CO: Board communication failure

The main control board and the display board have lost contact with each other. It is sometimes a temporary glitch but often points to a wiring or board fault.

May need a technician

By the FixByModel editorial team · Verified 2026-09 · Researched against manufacturer support & repair references (below)

Most likely causes

  1. Loose or damaged communication harness between boards
  2. Failed display (UI) board
  3. Failed main control board
  4. Moisture or corrosion at a connector
Before you start — unplug the refrigerator before working on it. Mind sharp metal edges, and never open the sealed refrigerant system — compressor, sealed-system and refrigerant work must be left to a qualified technician.

Step-by-step fix

1Power cycleUnplug the refrigerator or trip its breaker, wait about 5 minutes, then restore power to see if the boards re-establish communication.
2Check for moistureLook for signs of condensation or spills near the display and control board connectors.
3Do not force reset repeatedlyIf the code returns immediately after a power cycle, the part has failed rather than glitched.
4Get professional serviceHave a technician inspect the harness and test the boards; a control or display board may need replacement.

Still showing Er CO?

If you’ve worked through every step and Er CO keeps returning, an internal part likely needs testing and replacement. That’s a job for a qualified appliance technician, who can measure the suspect part against the service-manual spec before replacing it.

Which models this applies to

LG refrigerators. LG refrigerators with separate main and display control boards

FAQ

What does LG Er CO mean?

Board communication failure. The main control board and the display board have lost contact with each other. It is sometimes a temporary glitch but often points to a wiring or board fault.

What causes LG Er CO?

The most likely cause is loose or damaged communication harness between boards. Other causes include Failed display (UI) board; Failed main control board; Moisture or corrosion at a connector.

Can I fix LG Er CO myself?

Some checks are DIY, but this code often points to an internal component, so it may need a qualified technician.