LG · Refrigerator Moderate

Er CO — Communication error (main board ↔ display)

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

Keep using it?
Yes, with caution
DIY difficulty
Moderate
Verified against
lg.com ↗

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.

Why it happens

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

  • Broken/loose communication wire Harness through the door hinge gets damaged with door swings.
  • Display PCB failure Front display board failed.
  • Main control board failure Comm bus driver on the main PCB failed.
  • Loose connector at either board Vibration unseats the plug.

Replace your water filter

A clogged or overdue water filter is a common cause of low water and ice flow on LG refrigerators — they are meant to be changed about every 6 months. The OEM-style filter that fits most LG refrigerators is the LT1000P ($45-55 OEM, $18-28 compatible).

  • LG LT1000P refrigerator water filter OEM water filter
    Amazon →

Not sure which filter fits your model? See the full compatibility guide →

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.

  • Display PCB / UI board Common replacement
    Amazon →
  • Main control board Common replacement
    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 motor feedback fault Er dH Er dH — Defrost cycle exceeded time limit

All LG codes → All refrigerator codes →

Always unplug an appliance before servicing it. This guide is for informational purposes and is not a substitute for a qualified technician. Verified against manufacturer documentation: lg.com.