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Error code reference

LG Refrigerator Error Code Er Co2

Communication error between Micom of Sub PCB and Display Micom due to poor communication connection or poor…

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Communication error between Micom of Sub PCB and Display Micom due to poor communication connection or poor TR of Transmitter and Receiver Tx/Rx between display and sub board.

First step from the service manual

Check for loose connections, then check voltage Red to White/Red at CON101 Display for 12V.

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

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What Er Co2 means on a LG refrigerator

The Er Co2 error code on an LG refrigerator indicates a communication failure between the Sub PCB microcontroller (Micom) and the Display Micom. These two control boards exchange data continuously to coordinate temperature display, user inputs, and operational commands. When the signal between them breaks down or becomes unreliable, the refrigerator logs this error to alert the technician that the communication pathway has been compromised.

The root cause typically falls into one of two categories: a physical connection problem or a component-level failure in the transmitter/receiver (Tx/Rx) circuitry. The Tx/Rx circuit uses transistor-based signal transmission to pass data between the display board and the sub board. A failed or degraded transistor in this circuit can corrupt or block the data signal entirely. Poor solder joints, damaged connector pins, or a wire harness that has worked loose at CON101 on the display board are also frequent contributors.

The first diagnostic step is to inspect all wiring and connector seating between the display and sub board, paying close attention to CON101 on the display. After confirming connections are secure, measure the voltage between the Red wire and the White/Red wire at CON101. A correct reading should be approximately 12V DC. If voltage is absent or significantly low, the issue likely originates upstream at the sub board or power supply feeding that circuit. If voltage is present but the error persists, suspect a failed transistor or IC component within the Tx/Rx communication circuit on either board.

Source: manufacturer service documentation.

Common causes of Er Co2

  1. 01

    Loose or disconnected wiring at CON101

    Wiring / connection

    The connector at CON101 on the display board can work loose over time due to vibration or handling. Inspect the connector for bent pins, corrosion, or incomplete seating and reseat it firmly.

  2. 02

    Failed Tx/Rx transistor on display or sub board

    Part replacement

    The transistor responsible for transmitting or receiving the communication signal between the two boards can fail, breaking the data link. This requires component-level testing or board replacement to resolve.

  3. 03

    Absent or low 12V supply at CON101

    Part replacement

    If the voltage measured between Red and White/Red at CON101 is not approximately 12V DC, the display board is not receiving proper power for communication. This points to a fault in the sub board or its power supply circuit.

  4. 04

    Damaged wire harness between display and sub board

    Part replacement

    The wiring harness running between the two boards can develop breaks, shorts, or damaged insulation, especially near routing clips or hinges. Visually inspect the full harness length and test continuity on each wire.

  5. 05

    Faulty sub PCB or display PCB

    Part replacement

    If connections and voltage supply check out correctly but the error persists, either the sub board or the display board itself may have an internal failure in the communication circuitry requiring board replacement.

See the test procedure for each cause

Frequently asked questions about Er Co2

What does Er Co2 mean on a LG refrigerator?
Er Co2 indicates a communication error between the Sub PCB Micom and the Display Micom on your LG refrigerator. The two control boards have lost the ability to exchange data properly. This is usually caused by a loose wiring connection at the display board connector or a failure in the transistor-based Tx/Rx communication circuit between the boards.
Can I fix Er Co2 on my LG refrigerator myself?
A knowledgeable DIYer can start by unplugging the refrigerator and checking for loose or disconnected connectors between the display and sub board, specifically at the CON101 connector on the display. If reseating connections does not resolve the issue, diagnosing the 12V supply voltage and testing the Tx/Rx transistor circuit requires a multimeter and some familiarity with electronics. Board replacement is straightforward but confirming which board has failed first will save unnecessary parts costs.
Is it safe to keep using my refrigerator while Er Co2 is displayed?
Er Co2 reflects a control communication failure, which can affect the refrigerator's ability to regulate temperatures and respond to user commands properly. Running the unit in this state risks food spoilage if cooling control is compromised. It is best to address the error promptly rather than continuing normal use.
Will resetting my LG refrigerator clear the Er Co2 error?
A power reset by unplugging the refrigerator for a few minutes may temporarily clear the error if the cause was a transient communication glitch. However, if a loose connector, failed transistor, or board fault is present, the error will return shortly after the reset. A reset alone is not a repair and should be followed by proper diagnostics.
How much does it cost to repair an Er Co2 error on an LG refrigerator?
If the fix is simply reseating a loose connector, there is no parts cost involved. Replacing a display board or sub PCB typically runs anywhere from $80 to $250 or more depending on the specific model and parts sourcing. Adding a professional technician's labor will bring the total repair cost higher, generally in the range of $150 to $400 depending on your area and the parts required.

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