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Error code reference

LG Refrigerator Error Code Er CO

Communication failure

LG codesLG refrigerator codes

Communication failure — connection between main PCB and display PCB is faulty, snapping or short-circuit of lead wire, or poor transmitter/receiver parts between main PCB and display PCB.

First step from the service manual

Check lead wire connections between main PCB and display PCB; check TR and receiving parts.

The complete diagnostic procedure includes additional test steps, resistance specifications, wiring diagram references, and component test points.

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What Er CO means on a LG refrigerator

The Er CO error code on an LG refrigerator indicates a communication failure between the main control PCB and the display PCB. These two boards continuously exchange data signals to coordinate cooling functions, temperature settings, and user interface feedback. When that communication link is disrupted or degraded, the refrigerator detects the breakdown and triggers this code to alert the technician or user that the control system cannot function reliably.

The most common hardware causes involve the lead wire harness that runs between the two boards. A snapped wire, pinched conductor, or loose connector plug can interrupt the data signal entirely. Short circuits within the harness are also possible, particularly if a wire has been chafed against a sharp edge or exposed to moisture. Beyond the wiring, the transmitter and receiver components on each board handle the actual signal transmission. If a transistor, optocoupler, or similar transceiver component on either the main PCB or display PCB has degraded or failed, the communication link will drop even when the wiring itself is intact.

Diagnosis should begin with a thorough inspection of the lead wire harness connecting the two boards. Check each connector for corrosion, bent pins, or incomplete seating. Then trace the harness for any visible damage such as cuts, pinches, or burn marks. If the wiring checks out, the next step is evaluating the transmitter and receiver components on both boards, which may require measuring signal output or replacing the suspect PCB to confirm the fault.

Source: manufacturer service documentation.

Common causes of Er CO

  1. 01

    Loose or disconnected wire harness connector

    Wiring / connection

    The connector plug linking the main PCB and display PCB may have worked loose over time due to vibration. Reseating the connector firmly at both ends is the first check to perform.

  2. 02

    Damaged or broken lead wire

    Part replacement

    A wire in the harness between the two boards may be snapped, pinched, or broken internally. Inspect the full length of the harness for visible cuts, kinks, or chafing against cabinet edges.

  3. 03

    Short circuit in the wiring harness

    Part replacement

    Chafed insulation or moisture exposure can cause conductors in the harness to short against each other or against the chassis. Look for burn marks, corrosion, or signs of moisture intrusion along the harness route.

  4. 04

    Failed transmitter or receiver component on main PCB

    Part replacement

    The transceiver components on the main control board responsible for sending and receiving data signals can fail due to power surges or age. If wiring is intact, the main PCB may need to be tested or replaced.

  5. 05

    Failed transmitter or receiver component on display PCB

    Part replacement

    The display PCB contains its own receiving and transmitting components that can fail independently of the main board. If the main PCB tests good and wiring is sound, the display PCB is the next suspect.

See the test procedure for each cause

Frequently asked questions about Er CO

What does Er CO mean on a LG refrigerator?
Er CO indicates a communication failure between the main control PCB and the display PCB inside your LG refrigerator. The two boards use a wired data link to coordinate all functions, and this code appears when that link is broken or degraded. The cause can be a damaged wire harness, a loose connector, or a failed transmitter or receiver component on either board.
Can I fix the Er CO error myself?
A homeowner comfortable with basic appliance repair can start by unplugging the refrigerator and inspecting the wire harness connectors between the two boards for looseness or visible damage. Reseating a loose connector may resolve the code. However, if the wiring is damaged or a PCB component has failed, replacing a harness or control board typically requires some technical experience and the correct replacement parts.
Will resetting my LG refrigerator clear the Er CO code?
A reset by unplugging the unit for a few minutes may temporarily clear the code if the fault was caused by a momentary signal dropout. However, if there is physical damage to the wiring or a component on either board has failed, the code will return once power is restored. A reset is a reasonable first step, but a thorough inspection of the harness and PCB components is still necessary if the code reappears.
Is it safe to keep using my refrigerator while Er CO is displayed?
With an active Er CO error, the refrigerator may not respond correctly to temperature settings or operate its cooling system reliably, since the main PCB and display PCB cannot communicate properly. Continuing to run the unit in this state risks food safety due to unpredictable temperature control. It is best to address the fault promptly and avoid relying on the refrigerator to maintain safe temperatures until the issue is resolved.
How much does it cost to repair the Er CO error on an LG refrigerator?
Repair costs depend on the root cause. If only a wire harness needs to be replaced, parts and labor typically range from around $75 to $200. If a display PCB or main control PCB is required, costs can range from $150 to $400 or more depending on the specific board and labor rates in your area. Getting a diagnostic visit from a qualified technician first will help pinpoint the exact failed component before committing to a repair.

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