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Error code reference

LG Refrigerator Error Code Lc - Er

LOAD MICOM to MAIN MICOM communication error

LG codesLG refrigerator codes

LOAD MICOM to MAIN MICOM communication error — no response for 20 seconds after main MICOM received communication request from load MICOM, or option is not equivalent with the right value.

First step from the service manual

Recheck condition with oscilloscope (1GHz) after replacing Main and Panel PCB.

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

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What Lc - Er means on a LG refrigerator

The Lc - Er code on an LG refrigerator indicates a communication failure between the Load MICOM (microcontroller) and the Main MICOM. Specifically, the Main MICOM has sent or received a communication request from the Load MICOM but received no valid response for a continuous period of 20 seconds. This communication channel is a serial data link that coordinates control signals between the primary control board and secondary load-side circuitry. A second trigger condition also exists: the option configuration data stored in one board does not match the expected value on the other, meaning a mismatch in programmed parameters between the two controllers can also produce this fault.

The two microcontrollers involved are located on the Main PCB and the Panel PCB respectively. These boards exchange data continuously during normal operation to synchronize compressor load states, fan control, and display functions. When the handshake protocol times out or the option bytes are inconsistent, the refrigerator flags the Lc - Er fault to prevent undefined behavior from mismatched control logic.

Diagnosing this error requires more than a simple visual inspection. The recommended diagnostic approach involves replacing both the Main PCB and the Panel PCB, then re-evaluating the communication signal waveform using an oscilloscope rated at 1 GHz or higher. This level of signal verification is necessary because intermittent line noise, damaged signal traces, or faulty clock signals on the communication bus may not be visible through voltage measurements alone. If the waveform is clean and stable after board replacement, the fault is confirmed as a hardware failure on one or both original boards.

Source: manufacturer service documentation.

Common causes of Lc - Er

  1. 01

    Faulty Main PCB

    Part replacement

    The Main MICOM on the primary control board may have failed or developed corrupted firmware, preventing it from responding to or interpreting communication requests from the Load MICOM. This is often confirmed after board replacement resolves the error.

  2. 02

    Faulty Panel PCB

    Part replacement

    The Panel PCB houses the Load MICOM and initiates communication requests to the Main board. A failed or damaged Panel PCB can cause the 20-second timeout condition, triggering the Lc - Er fault.

  3. 03

    Option configuration mismatch between boards

    Wiring / connection

    If a replacement board with different programmed option values is installed, the two MICOMs may disagree on system parameters. This mismatch alone is enough to trigger the Lc - Er code without any hardware defect being present.

  4. 04

    Damaged or loose wiring harness between PCBs

    Wiring / connection

    The communication bus between the Main and Panel boards relies on a wiring harness and connectors. A loose connection, pinched wire, or corroded terminal on this harness can interrupt the serial data signal and cause the timeout error.

  5. 05

    Signal line noise or damaged PCB traces

    Part replacement

    Electrical interference or physical damage to the communication signal traces on either board can corrupt the data being transmitted. This type of fault may only be detectable with a 1 GHz oscilloscope examining the waveform quality on the communication bus.

See the test procedure for each cause

Frequently asked questions about Lc - Er

What does Lc - Er mean on a LG refrigerator?
Lc - Er indicates a communication error between the Load MICOM and the Main MICOM on your LG refrigerator. The Main MICOM did not receive a valid response from the Load MICOM within 20 seconds, or the option configuration values between the two boards do not match. This is a control board communication fault that typically requires PCB-level diagnosis and often board replacement.
Can I fix the Lc - Er error myself?
Basic checks like inspecting the wiring harness connectors between the Main and Panel PCBs are within reach for a skilled DIYer. However, the definitive diagnostic step requires replacing both the Main PCB and Panel PCB and then verifying the communication signal with a 1 GHz oscilloscope, which is specialized equipment most homeowners do not have. Professional service is strongly recommended for this fault code.
Will resetting my LG refrigerator clear the Lc - Er code?
A power reset may temporarily clear the display, but the code will return if the underlying communication fault between the two control boards still exists. Because the error triggers after a 20-second timeout with no valid response, any persistent hardware or configuration issue will cause it to reappear shortly after power is restored.
Is it safe to keep using my refrigerator while the Lc - Er code is displayed?
A communication failure between the Main and Load MICOMs means the refrigerator cannot reliably coordinate compressor and fan control. Food safety may be at risk if cooling is compromised. It is advisable to check internal temperatures and transfer perishables if the refrigerator does not appear to be cooling normally while this code is active.
How much does it cost to repair the Lc - Er error on an LG refrigerator?
Repair costs vary depending on which component has failed and local labor rates. A Main PCB replacement typically ranges from around 150 to 350 dollars for the part alone, and a Panel PCB replacement can add another 80 to 200 dollars. With professional labor included, total repair costs commonly fall between 250 and 600 dollars, depending on whether one or both boards need to be replaced.

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