LG Refrigerator Error Code Er CO — Communication Error
What this means
The Er CO error code indicates a communication failure between the refrigerator's main control board and the display (user interface) board. These boards communicate via a wiring harness, and a loss of communication means the display cannot send commands to the main board or receive status updates. This can be caused by a loose wire harness, a failed display board, or a faulty main control board.
Alternate codes: CO
Step-by-step fix
3 stepsPower cycle the refrigerator
Unplug the refrigerator for 10 minutes, then plug it back in. A temporary communication glitch can sometimes be cleared with a reset.
If the refrigerator beeps and the error clears but returns after a few minutes, the connection is intermittent.
Check the wire harness between boards
Unplug the refrigerator. The display board is behind the front panel (on the door of French door models, or on the top front). The main board is usually at the rear bottom. Check the wire harness or ribbon cable connecting them — ensure both ends are firmly seated.
On French door models, the wire harness passes through the door hinge area and can be pinched or damaged when the door is removed during moving.
Inspect both boards for damage
Open the housings of both the display board and main control board. Look for burned components, corrosion, or water damage. Any visible damage indicates the board needs replacement.
Water from a leaking ice maker or defrost drain can drip onto the main control board and cause corrosion.
When to call a professional
Diagnosing which board has failed requires testing signal outputs, which is best done by a technician. Replacing the wrong board is costly. A professional can also check for wiring damage inside the door hinge area.
Information compiled from manufacturer service manuals, official troubleshooting documentation, and appliance repair industry resources. This guide is for informational purposes only — always consult a qualified technician for complex repairs.
Learn more about our sourcesParts you may need
Main Control Board
Part #EBR78940616 · $100–$250
If main board is damaged or confirmed faulty
Display Control Board
Part #EBR78940508 · $80–$180
If display board is damaged or confirmed faulty
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