What does LG Refrigerator CO Error Code - Causes & Fix mean?

CO means the main board and display board are not talking. Check the harness between them, then replace the failed board.

How do I fix LG Refrigerator CO Error Code - Causes & Fix?

Follow the step-by-step diagnosis below. The most likely fix is identified by checking power, sensor resistance, and control-board signals in order — using a multimeter and the part numbers documented in the parts reference table.

Can I keep running the equipment with this fault active?

Generally no. Faults on Appliance units are emitted when a sensor, safety, or control circuit is outside its operating envelope. Running through an active fault risks compressor, heater, or control-board damage. Diagnose and clear the fault first.

What part is most commonly replaced for LG Refrigerator CO Error Code - Causes & Fix?

The most frequently replaced parts for LG Refrigerator CO Error Code - Causes & Fix are listed in the Parts Reference section of this guide with OEM part numbers and typical price ranges. Check the table for direct replacements.

Is LG Refrigerator CO Error Code - Causes & Fix a DIY repair or do I need a technician?

Sensor swaps, fan motor replacements, and condenser cleaning are typical DIY-level repairs. Anything involving refrigerant, gas, or high-voltage (>240V) work requires a licensed technician for both safety and code-compliance reasons.

LG Refrigerator CO Error Code - Causes & Fix

LG Refrigerator CO Error Code — What It Means

The CO code (shown as Er CO) is a communication error between the main control board and the display board. The two boards exchange data, and when that link drops the unit posts CO and controls or the display may stop responding.

The cause is usually a loose or damaged harness between the boards, a failed display board, or a failed main board. Wiring gets checked first because a connector issue is cheaper to fix than a board.

Jump to Fix

Common Causes

Loose board to board harness A connector that backed out between the main board and the display breaks the data link and trips CO.
Damaged wiring A pinched or chafed harness between the two boards interrupts communication.
Failed display board A display control board that stops responding leaves the main board with no answer.
Failed main control board A main board that cannot drive the communication line posts CO even with a good display.
Power or grounding glitch A brief power fault can drop the link, which a reset sometimes clears.

Step-by-Step Fix

Unplug the refrigerator or trip the breaker, wait 5 minutes, then restore power to see if CO clears.
Locate the harness that runs between the main control board and the display board.
Inspect both connectors for loose pins, corrosion, or backed out terminals.
Reseat each connector firmly and clean any corrosion you find.
Trace the harness for pinch points or chafing and repair any damaged section.
If the wiring is sound, replace the display board and recheck for the code.
If CO remains after a new display board, replace the main control board.

Parts Often Needed

Part	Notes
LG refrigerator display control board	Amazon \| Match by model number. This is the board behind the user controls and readout.
LG refrigerator main control board	Amazon \| Replace after the wiring and display board are ruled out.
Board to board wiring harness	Amazon \| Only if the existing harness is pinched or corroded.

When to Call a Pro

Call a technician if CO stays after you reseat the harness, since telling which of the two boards failed often needs swap testing. A tech can confirm the bad board and avoid replacing the wrong one.