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Error code reference

LG Refrigerator Error Code R1 R2 R3 R4

Faulty R sensor

LG codesLG refrigerator codes

Faulty R sensor - The refrigerator sensor is open or short circuited, compressor cycles 15 min ON / 15 min OFF.

First step from the service manual

Check refrigerator sensor resistance and voltage at Point A (normal 0.5V-4.5V, short-circuited 0V, open 5V). Replace sensor if faulty.

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

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  • Step-by-step tests with expected resistance, voltage, and continuity values
  • Wiring diagram references and connector pinouts from the OEM service manual
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What R1 R2 R3 R4 means on a LG refrigerator

The R1, R2, R3, and R4 error codes on LG refrigerators all indicate a fault with the refrigerator compartment temperature sensor (R sensor). This sensor is a thermistor that continuously monitors the internal temperature of the refrigerator section and sends voltage-based signals to the control board. The control board reads a normal operating voltage at Point A between 0.5V and 4.5V, which corresponds to varying resistance levels across a range of temperatures. When the sensor shorts out, the voltage at Point A drops to 0V, and when the circuit opens completely, the voltage rises to 5V. Either condition triggers an R-series fault code.

When this fault is active, the refrigerator enters a protective operating mode where the compressor runs on a fixed 15-minute ON and 15-minute OFF duty cycle. This default cycle prevents the compressor from running continuously without accurate temperature feedback, which could cause over-cooling or component damage. However, it also means the refrigerator cannot maintain precise temperature control, so food safety can become a concern if the fault is not addressed promptly.

The most common causes of R sensor faults are physical damage to the sensor or its wiring harness, moisture intrusion leading to corrosion at the connector, or outright thermistor failure. Sensor resistance values shift outside acceptable range as thermistors age or are exposed to prolonged moisture. Because the diagnostic process involves measuring both voltage at Point A and sensor resistance directly, a technician can quickly distinguish between a failed sensor and a wiring or connector issue before ordering replacement parts.

Source: manufacturer service documentation.

Common causes of R1 R2 R3 R4

  1. 01

    Failed thermistor sensor

    Part replacement

    The thermistor itself has failed due to age or moisture exposure, causing its resistance to fall outside the normal range. This will show as 0V (shorted) or 5V (open) at Point A during testing.

  2. 02

    Open circuit in sensor wiring

    Wiring / connection

    A break in the wiring harness between the sensor and the control board causes the voltage at Point A to read 5V. Inspect the wiring run for pinched, cut, or disconnected sections.

  3. 03

    Short circuit in sensor wiring

    Wiring / connection

    A wire in the sensor circuit contacting ground or another conductor pulls the Point A voltage to 0V. Visually inspect the harness for damaged insulation or areas where wiring contacts metal cabinet edges.

  4. 04

    Corroded or loose sensor connector

    Wiring / connection

    Moisture in the refrigerator compartment can cause corrosion at the sensor connector, increasing resistance or breaking continuity entirely. Check the connector pins for oxidation and ensure the connector is fully seated.

  5. 05

    Control board fault misreading sensor signal

    Part replacement

    In less common cases, the control board input circuit for the R sensor may be faulty, causing incorrect voltage readings even when the sensor and wiring are intact. This should be considered only after the sensor and wiring have been confirmed good.

See the test procedure for each cause

Frequently asked questions about R1 R2 R3 R4

What does R1 R2 R3 R4 mean on a LG refrigerator?
These codes all indicate a fault with the refrigerator compartment temperature sensor. The sensor is either shorted, causing 0V at the diagnostic test point, or has an open circuit, causing 5V at that same point. The normal operating range at Point A is 0.5V to 4.5V. When this fault is present, the compressor defaults to a 15-minute ON and 15-minute OFF cycle because the control board cannot receive accurate temperature data.
Can I fix the R1 R2 R3 R4 error myself on my LG refrigerator?
A knowledgeable DIYer can diagnose this fault by measuring voltage at Point A in the sensor circuit and checking the sensor resistance directly. If the sensor wiring or connector is visibly damaged or corroded, that can sometimes be repaired without special tools. However, if the thermistor itself has failed, a replacement sensor will be needed, and the part must be compatible with your specific LG model.
Is it safe to keep using my LG refrigerator while showing the R1 R2 R3 R4 error?
The refrigerator will continue to run in a failsafe mode with the compressor cycling 15 minutes on and 15 minutes off, but it will not accurately regulate temperature. This means the interior temperature may not stay within the safe range for perishable food. It is advisable to address the fault promptly and monitor food temperatures closely in the meantime.
Will resetting my LG refrigerator clear the R1 R2 R3 R4 error code?
A power reset may temporarily clear the displayed code, but if the underlying sensor fault is still present, the code will return once the control board re-evaluates the sensor signal. The fault must be corrected by repairing or replacing the faulty sensor or wiring before the error will clear permanently.
How much does it cost to repair the R1 R2 R3 R4 error on an LG refrigerator?
If only the temperature sensor needs replacement, parts costs typically range from around $15 to $60 depending on the model, with professional labor adding $80 to $200 or more depending on your location. If the fault turns out to be a wiring or connector issue, repair costs may be lower since no major parts are required. Control board replacement, if needed, is significantly more expensive and can range from $150 to $400 or higher for parts alone.

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