LG Refrigerator Error Code Er CO: Communication Error Between Main PCB and Display
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What Error Code Er CO Means
The Er CO code indicates the main control board and the display board have lost communication with each other. These two boards exchange data through a ribbon cable or wire harness. If that link breaks, the display cannot send your temperature commands to the main board, and the main board cannot report status back. The refrigerator often continues running at default settings, but you lose all user controls.
Common Causes
Loose or damaged ribbon cable
The flat ribbon cable connecting the display board to the main board works loose from vibration or gets crimped when the door is repeatedly opened and closed. A single broken trace in the ribbon kills communication.
Failed display board
The display board's communication IC fails. The display goes dark or shows partial segments along with the Er CO code.
Failed main control board
The communication circuit on the main PCB has a blown component or cracked solder joint. The display works, but the main board does not respond.
Power surge damage
A voltage spike damages the communication circuitry on one or both boards. This often happens after a power outage or lightning strike.
How to Fix It
- 1
Power-cycle the refrigerator
Unplug the refrigerator for 5 minutes. Plug it back in. A brief communication glitch clears with a full reset. If Er CO returns within a few minutes, the problem is hardware-related.
- 2
Reseat the display board ribbon cable
Open the refrigerator door. The display panel is on the top of the door or on the front face. Remove the display housing (usually 2-4 Phillips screws or plastic clips). Locate the ribbon cable connection on the back of the display board. Gently pull it out and reinsert it firmly until it clicks or seats fully. Reassemble the housing.
Unplug the unit before handling any circuit board connections.
- 3
Inspect the wire harness along the door hinge
On French-door and side-by-side models, the communication harness runs through the top door hinge. Open and close the door while watching the harness. Look for worn insulation, pinched wires, or broken conductors at the hinge pass-through. Repair damaged wires with solder and heat-shrink tubing.
- 4
Check the main control board connector
Remove the rear lower access panel. Locate the main control board. Find the connector labeled for the display or UI board (check your model's tech sheet taped inside the fridge compartment). Disconnect and reconnect it. Look for burn marks or corrosion on the pins.
- 5
Swap-test the display board
If you have access to a known-good display board (same model), swap it in. If communication restores, the original display board is faulty. If Er CO persists, the main control board is the problem. This step avoids buying the wrong part.
When to Call a Professional
Communication errors involve circuit boards and ribbon cables that are easy to damage further. If a power-cycle and reseating connectors do not fix the problem, call a licensed technician. TruePro's $59 diagnostic fee gets credited toward the repair. We carry common LG display and main control boards on our trucks for same-day repairs. All work is backed by a 90-day parts and labor warranty. CA License #51112. Call 877-378-3111. First-time customers take 15% off labor with code NEW15.
Estimated Repair Cost
| Option | Estimated Cost |
|---|---|
| DIY (parts only) | $50 - $180 |
| Professional repair | $200 - $450 |
DIY cost covers a display board or ribbon cable. Pro range includes diagnosis and board replacement. If both boards need replacement, expect $450-$650 total.
See full refrigerator repair cost breakdown βLG Refrigerator Er CO β FAQ
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