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Error code reference

LG Refrigerator Error Code CO

Communication Error

LG codesLG refrigerator codes

Communication Error - no signal for communication between main and display PCB; may be caused by lead wire short between main and display PCB, transmission TR and receiving part failure.

First step from the service manual

Check for loose connections; measure Orange to Black voltage at CON101 display (should be 12V).

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

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What CO means on a LG refrigerator

The CO error code on an LG refrigerator indicates a communication failure between the main control PCB and the display PCB. These two boards exchange data signals continuously to coordinate functions like temperature control, fan operation, and user interface feedback. When that signal is interrupted or lost entirely, the unit flags the CO code to alert the technician that the communication link has broken down. The error specifically points to a missing or corrupted signal on the communication line rather than a general power failure.

The most common hardware causes include a shorted or damaged lead wire running between the main and display PCBs, a failed transmission transistor (TR) on the sending side, or a defective receiving component on the display board. A wiring short can corrupt the data signal even if power is still present at the boards. The first diagnostic step is to inspect the connector at CON101 on the display PCB and measure the voltage between the Orange and Black wires. A healthy communication circuit should read 12V at that point. A reading significantly below 12V or no voltage at all points toward a wiring fault, a failed supply path, or a board-level component failure.

If the voltage at CON101 measures correctly at 12V but the CO code persists, the fault likely lies within the transmitting or receiving circuitry on one of the PCBs themselves. Loose or corroded connector pins are also a frequent contributor and should be reseated and inspected before replacing any components. A systematic approach starting at the connectors, then the wiring harness, and finally the boards will help isolate the defective part efficiently.

Source: manufacturer service documentation.

Common causes of CO

  1. 01

    Loose or disconnected wiring connector

    Wiring / connection

    The connector at CON101 on the display PCB can work loose over time, interrupting the communication signal. Inspecting and firmly reseating the connector is the recommended first step before any further diagnosis.

  2. 02

    Shorted lead wire between main and display PCB

    Part replacement

    A short circuit in the wiring harness that runs between the two boards can corrupt or eliminate the communication signal entirely. Visually inspect the harness for pinched, frayed, or melted insulation and test continuity across the wire run.

  3. 03

    Incorrect voltage at CON101

    Wiring / connection

    The Orange to Black wire voltage at CON101 should measure 12V under normal conditions. A reading below this value indicates a supply or wiring problem that is preventing the communication circuit from functioning properly.

  4. 04

    Failed transmission transistor on main PCB

    Part replacement

    The transmission TR component on the main control board is responsible for sending the communication signal to the display. If this transistor fails, no signal will reach the display PCB regardless of wiring condition.

  5. 05

    Defective receiving component on display PCB

    Part replacement

    If the receiving side of the display PCB is damaged, it cannot process the signal sent from the main board even when the wiring and transmission components are functioning correctly. This typically requires display board replacement.

See the test procedure for each cause

Frequently asked questions about CO

What does CO mean on a LG refrigerator?
CO stands for Communication Error and indicates that the main control PCB and the display PCB have lost their communication signal. The error can be caused by a loose connector, a shorted wiring harness, or a failed component on either board. The first place to check is the CON101 connector on the display PCB, where the Orange to Black wire voltage should read 12V. If that voltage is missing or low, the wiring or power supply path needs further investigation.
Can I fix the CO error myself on my LG refrigerator?
Some causes of the CO error are within reach of a careful DIYer. Checking for loose connectors at CON101 and inspecting the wiring harness for visible damage require no special tools. However, diagnosing a failed transmission transistor or a defective PCB requires electrical testing skills and proper equipment, so those steps are better handled by a qualified technician.
Is it safe to keep using my refrigerator when it shows the CO error?
A CO error means the main board and display board are not communicating correctly, which can affect the refrigerator's ability to regulate temperature and respond to control inputs. It is not advisable to rely on the unit for food storage while this error is active, as normal operation cannot be confirmed until the fault is resolved.
Will resetting my LG refrigerator clear the CO error?
A power reset may temporarily clear the CO code if it was triggered by a transient signal glitch, but if the underlying fault persists, such as a loose connector or a shorted wire, the error will return. A reset is worth trying after reseating connectors, but a recurring CO code requires proper diagnosis and repair of the root cause.
How much does it cost to repair the CO error on a LG refrigerator?
Repair costs depend on the specific cause. If only a wiring harness repair or connector reseating is needed, costs are generally lower, typically in the range of $75 to $200 for a service call. If a main control PCB or display PCB requires replacement, parts and labor combined can range from $200 to $500 or more depending on the model and local labor rates.

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