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Severity: Moderate

LG Refrigerator Error Er CO – Causes & Fix

The display board and the main control board have stopped talking to each other over their wiring harness.

At a glance

Severity: 3/5 – Moderate3/5

Severity: Moderate

Meaning
Communication Error – Main Board and Display
Typical repair cost
$0–$500
DIY difficulty
Moderate

On LG refrigerators the buttons and display live on one circuit board, usually in the door or on the dispenser, while the main control board that runs the compressor, fans and defrost sits in the cabinet. The two exchange data constantly over a thin harness that, on door-mounted displays, runs through the top hinge. LG shows Er CO (or E CO) when that link fails and notes that unstable power can trigger it temporarily. If a power reset doesn't clear it, the cause is usually a damaged harness at the hinge, moisture at the display or a failed board. The fridge normally keeps cooling on its last settings, but you lose control of temperatures, the dispenser and the ice maker.

How it looks on the display

LG Refrigerator / Freezer display showing error Er CO

Model families & display variants

Model familyShowsNote
French-door and side-by-side models with display in the doorEr COEr on one readout, CO on the other; the harness runs through the upper hinge of that door.
Models with one panel displayE COLG lists E CO as the same communication error.
Models with the control panel inside the fridgeCONo hinge harness; check the connector behind the panel and the main board plugs.

Safety first · Consult a professional

Unplug the refrigerator before removing the hinge cover or any board cover. The harness and boards carry low-voltage signals, but the main board also switches line voltage to the compressor and heaters.

  • Unplug the appliance or switch off the breaker before opening any panel. Mains voltage can kill.

Symptoms

  • Er CO or E CO on the display, sometimes flashing or with a chime
  • Buttons don't respond; temperatures can't be changed
  • Water and ice dispenser dead or working only intermittently
  • Display flickers or goes blank when the door is opened or closed
  • Fridge and freezer still cool, at least for a while

Possible causes

Ranked by how often each cause is behind this code (editorial estimate).

  1. Harness chafed or cracked at the top door hinge where it flexes with every opening 30%
  2. Temporary glitch from a power surge, brownout or outage 20%
  3. Moisture in the display or dispenser area (drip tray overflow, condensation) 15%
  4. Display board failed 15%
  5. Main control board failed 15%
  6. Connector loosened at the main board after the fridge was moved 5%

Fix it step by step

Diagnostic flow: Er CO1Reset the power once2Do the door-swing test3Inspect the top hinge harness4Rule out moisture at the display5Reseat the main board plugs6Hand it to a technician

  1. Reset the power once

    Unplug the refrigerator or switch off its breaker for about five minutes, as LG suggests, then restore power. Plug it into a wall outlet rather than a power strip; if it's on a GFCI outlet that trips, have that looked at.

  2. Do the door-swing test

    With the fridge powered, slowly open and close the door that carries the display while watching it. If the code appears, flickers or disappears at certain door angles, the wires in the top hinge are breaking.

  3. Inspect the top hinge harness

    Unplug the unit and remove the plastic cover over the top hinge of the display door. Check the connector for a full latch and look along the wires for flattened, chafed or broken spots where they bend into the door.

    Tools: Screwdriver, Flashlight

  4. Rule out moisture at the display

    Look for water in the dispenser drip tray, stains below the control panel or condensation behind the dispenser cover. If the area is wet, leave the fridge unplugged with the door open for several hours so the board can dry before you test again.

    Tools: Towels & shallow pan, Flashlight

  5. Reseat the main board plugs

    Depending on the model, the main board sits behind a cover at the lower back or on top of the cabinet toward the rear. With the power off, press each connector firmly home, especially if the fridge was recently moved or delivered.

    Tools: Screwdriver

  6. Hand it to a technician

    If the harness is intact and dry but the code stays, the technician checks the data and supply lines at both ends to decide whether the display or the main board is at fault – guessing and buying boards gets expensive.

    Tools: Multimeter

How to reset Er CO

  1. Unplug the refrigerator or switch off its breaker for about 5 minutes
  2. Restore power and wait for the display to come back up
  3. If Er CO is still there or returns, the link between the boards is physically damaged and needs service

Where the parts are

Refrigerator: evaporator fan, defrost heater and compressor – Er CO123456
Refrigerator: evaporator fan, defrost heater and compressor
  1. 1Evaporator fan
  2. 2Defrost heater
  3. 3Temperature sensor
  4. 4Door switch
  5. 5Compressor
  6. 6Condenser

Repair options & costs

RepairDIY?Estimated cost
Power reset and connector reseat Yes $0
Hinge harness repair by a technician No $150–$300
Display board replacement No $200–$400
Main control board replacement No $250–$500

Rough US estimates; technician call-out fees vary by region. Not a quote.

When to call a technician

Call LG service or a technician if Er CO survives a power reset, if the door-swing test shows a broken hinge harness, or if the fridge starts warming up. A board-to-board fault can also leave the compressor or fans without commands, so keep a thermometer in both compartments until it is repaired.

Frequently asked questions

Will my fridge keep cooling with Er CO?

Usually yes, on the settings it had before the error. Check with a thermometer: the fridge should stay at 40°F or below and the freezer near 0°F. If temperatures drift, treat it as urgent.

Why did Er CO show up after a power outage?

A surge or unstable voltage can interrupt the data link between the boards for a moment. That's why LG suggests a power reset first; if the code clears and stays away, no repair is needed.

Is it the display or the main board?

Either can fail, and so can the wiring between them. A technician measures the signals at both ends before replacing anything, which avoids buying the wrong board.

Could a leaking dispenser cause this?

Yes. Water that gets behind the dispenser can reach the display board and its connector. Drying it out sometimes clears the code; corrosion that stays usually means a new display board.

Sources