Er CO Moderate Moderate DIY

LG Refrigerator Er CO — Communication error (main board ↔ display)

LG Refrigerator · Error code Er CO

What Er CO Means

The main control board and the door/dispenser display PCB lost communication. Display may show Er CO with no other functionality.

Symptoms

  • Er CO on display
  • Dispenser controls non-responsive
  • Temperature setpoints won't change
  • Cooling may still operate normally

Common Causes

1
Broken/loose communication wire

Harness through the door hinge gets damaged with door swings.

2
Display PCB failure

Front display board failed.

3
Main control board failure

Comm bus driver on the main PCB failed.

4
Loose connector at either board

Vibration unseats the plug.

How to Fix It

  1. Unplug for 5 minutes and restore power — clears soft comm faults.
  2. If Er CO returns, unplug again and remove the rear access cover.
  3. Inspect the harness between main PCB and display, especially at the hinge.
  4. Reseat connectors at both ends of the comm bus.
  5. Replace the display PCB first if visibly damaged or partially lit.
  6. If still no fix, replace the main control board.

Parts You May Need

If diagnosis points to a failed part, these are the common replacements. As an Amazon Associate we earn from qualifying purchases.

Common replacement Display PCB / UI board View on Amazon→ Common replacement Main control board View on Amazon→

More LG Refrigerator Codes

22 22 — Compressor relay / inverter control fault 33 33 — Compressor / defrost test fault 67 67 — Door open / not fully closed 88 88 — Power-on display test (not a fault) Er CF Er CF — Condenser Fan Fault Er CO Er CO — Compressor / Communication Fault

All LG codes → All refrigerator codes →

Verified against manufacturer documentation: lg.com

Always unplug an appliance before servicing it. This guide is for informational purposes and is not a substitute for a qualified technician.