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Error code reference

LG Refrigerator Error Code CO 1

Communication error between Top Display and Dispenser Display PCBs.

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Communication error between Top Display and Dispenser Display PCBs.

First step from the service manual

Check for loose connections, then check voltage between Green and Pink wires on Top Display.

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

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What CO 1 means on a LG refrigerator

The CO 1 error code on an LG refrigerator signals a communication failure between the Top Display PCB and the Dispenser Display PCB. These two control boards communicate continuously through a data line, and when that signal is interrupted or corrupted, the refrigerator triggers CO 1 to alert that the two boards can no longer exchange information reliably. This communication path is critical for coordinating dispenser functions, temperature display, and user interface inputs.

The most important first diagnostic step is to check for loose or disconnected wiring between the two boards. The specific test point to focus on is the voltage between the Green and Pink wires on the Top Display connector. If voltage at those wires is outside the expected range, the issue may be with the Top Display PCB itself, the wiring harness, or the power supply feeding that circuit. A loose connector can cause intermittent CO 1 errors that come and go, while a failed board or broken wire typically produces a persistent fault.

Common causes include damaged wire harnesses, corroded or improperly seated connectors, and failed PCBs. Because this fault involves two separate boards communicating over a shared line, either board can be the source of the problem. Diagnosis should proceed from the simplest checks first: inspect connectors for corrosion or bent pins, verify the wire harness has no pinch points or breaks, and confirm voltage at the Green and Pink wires before replacing any components.

Source: manufacturer service documentation.

Common causes of CO 1

  1. 01

    Loose or disconnected wiring harness connector

    Wiring / connection

    A connector between the Top Display PCB and the Dispenser Display PCB may have worked itself loose, interrupting the communication signal. Inspect all connectors on both boards for secure seating and check for any signs of the harness being pulled or pinched.

  2. 02

    Corroded or damaged connector pins

    Wiring / connection

    Moisture or age can corrode the pins inside the harness connectors, increasing resistance on the communication line and causing signal loss. Look for green or white buildup on the pins and check that none are bent or pushed back in the housing.

  3. 03

    Broken or shorted wire in the harness

    Part replacement

    A wire in the harness connecting the two boards may be broken internally or shorted against the refrigerator chassis, particularly if the harness passes through a tight area or was pinched during service. Check the Green and Pink wires specifically for continuity and proper voltage at the Top Display connector.

  4. 04

    Failed Dispenser Display PCB

    Part replacement

    If wiring and connectors check out and voltage at the Top Display is correct, the Dispenser Display PCB may have failed and is no longer responding to communication from the Top Display. This typically requires board replacement to resolve.

  5. 05

    Failed Top Display PCB

    Part replacement

    If the Top Display PCB is not producing the correct voltage on the Green and Pink wires, the board itself may be defective and unable to maintain the communication link. Voltage testing at those wires helps isolate this as the root cause before replacing the board.

See the test procedure for each cause

Frequently asked questions about CO 1

What does CO 1 mean on a LG refrigerator?
CO 1 on an LG refrigerator indicates a communication error between the Top Display PCB and the Dispenser Display PCB. These two boards need to continuously exchange signals to coordinate the display and dispenser functions. When that communication is lost or disrupted, the refrigerator logs this code. The fault can stem from loose connections, damaged wiring, or a failed control board.
How do I fix a CO 1 error on my LG refrigerator?
Start by unplugging the refrigerator and inspecting the wiring connectors between the Top Display PCB and the Dispenser Display PCB for loose, corroded, or damaged pins. Reseat all connectors firmly and check the wire harness for any visible breaks or pinching. If connections are secure, the next step is to test voltage between the Green and Pink wires on the Top Display connector with the unit powered. If voltage is incorrect, further board-level diagnosis or replacement may be necessary.
Will resetting my LG refrigerator clear the CO 1 error?
A power reset by unplugging the refrigerator for a few minutes may temporarily clear the CO 1 code if the fault was caused by a momentary signal disruption. However, if the underlying cause is a loose connection, damaged wire, or faulty PCB, the error will return once the refrigerator powers back up. A reset alone is not a repair and should be followed by proper diagnosis.
Is it safe to use my LG refrigerator when CO 1 is displayed?
A CO 1 error affects the communication between the display and dispenser boards, which can impact the dispenser and the control interface. The refrigerator may still cool food during this fault, but dispenser functions may not work correctly and temperature adjustments through the display may not register. It is best to address the error promptly to ensure full and reliable operation.
How much does it cost to repair a CO 1 error on an LG refrigerator?
If the fix is simply reseating a loose connector, there may be no parts cost, only a service call fee which typically ranges from $75 to $150 depending on your area. If the wiring harness needs replacement, parts and labor together can range from $100 to $250. Replacing one of the control boards is more involved, with total repair costs generally ranging from $200 to $450 or more depending on which board has failed and local labor rates.

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