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Error code reference

LG Refrigerator Error Code FZ-Sensor Error

Sensor system in freezer compartment has error (separation, contact error, disconnection, short circuit, or…

LG codesLG refrigerator codes

Sensor system in freezer compartment has error (separation, contact error, disconnection, short circuit, or temperature out of range above 149°F/65°C or below -58°F/-50°C).

First step from the service manual

Check voltage at MAIN PCB CN30-3 to CN76-1; should be between 4.5V and 1.0V.

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

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What FZ-Sensor Error means on a LG refrigerator

The FZ-Sensor Error on an LG refrigerator indicates a fault within the freezer compartment temperature sensor circuit. This sensor, commonly a negative temperature coefficient (NTC) thermistor, feeds real-time temperature data to the main PCB so the control board can regulate the compressor and evaporator fan operation. When the board detects a reading outside its acceptable range, above 149°F (65°C) or below -58°F (-50°C), or detects a circuit anomaly such as an open circuit, short circuit, or poor connector contact, it triggers this error code to protect the system from operating with faulty temperature data.

The first diagnostic step is to measure voltage at the main PCB between connector CN30-3 and CN76-1. A properly functioning sensor circuit will produce a voltage that falls between 1.0V and 4.5V, varying with the actual freezer temperature. A reading at or near 0V typically indicates a short circuit in the sensor or wiring, while a reading at or near 5V suggests an open circuit or complete disconnection. Readings outside the 1.0V to 4.5V window that do not correspond to a realistic freezer temperature point to a failed sensor.

Beyond the sensor itself, this error can originate from damaged wiring harnesses, corroded or loose connector pins at the PCB or sensor terminals, or a failed main PCB that cannot correctly interpret sensor signals. Physical damage from ice buildup around the sensor harness is a common real-world cause, as is connector corrosion from moisture exposure inside the freezer compartment.

Source: manufacturer service documentation.

Common causes of FZ-Sensor Error

  1. 01

    Failed or out-of-range freezer temperature sensor

    Part replacement

    The NTC thermistor itself may have failed, causing its resistance to fall outside the range that produces a 1.0V to 4.5V signal at the PCB. This is the most frequent cause and can be confirmed by measuring sensor resistance at a known temperature.

  2. 02

    Loose or disconnected sensor connector

    Wiring / connection

    The connector at the sensor terminal or at PCB connector CN30-3 or CN76-1 may have vibrated loose or been partially dislodged. Inspect both ends of the wiring harness for connectors that are not fully seated.

  3. 03

    Damaged or pinched wiring harness

    Part replacement

    The wiring between the sensor and the main PCB can be pinched by shelving, ice buildup, or door components, causing an intermittent open circuit or short. Visually trace the harness for chafing, kinks, or ice encasement.

  4. 04

    Corroded connector pins

    Wiring / connection

    Moisture inside the freezer can corrode the pin contacts at either end of the sensor harness, increasing resistance and producing an erratic or out-of-range voltage signal at the PCB.

  5. 05

    Faulty main PCB

    Part replacement

    If the sensor and all wiring check out correctly and the voltage at CN30-3 to CN76-1 is still outside the 1.0V to 4.5V range, the main PCB may be unable to correctly process the sensor signal, indicating a board-level failure.

See the test procedure for each cause

Frequently asked questions about FZ-Sensor Error

What does FZ-Sensor Error mean on a LG refrigerator?
The FZ-Sensor Error means the refrigerator has detected a fault in the freezer compartment temperature sensor circuit. The error is triggered when the sensor signal falls outside the valid voltage range of 1.0V to 4.5V at the main PCB, or when the reported temperature exceeds 149°F (65°C) or drops below -58°F (-50°C). Possible causes include a failed sensor, a wiring disconnection, a short circuit, or a corroded connector.
Can I fix the FZ-Sensor Error myself?
Some causes of this error are DIY-accessible. Start by checking that the sensor connector is fully seated at both the sensor end and at the main PCB connectors CN30-3 and CN76-1. If you have a multimeter, you can measure the voltage across those connectors and test sensor resistance to determine whether the sensor or the wiring is at fault. Replacing the sensor is a moderate-difficulty repair, but main PCB replacement is generally best left to a technician.
Is it safe to keep using my refrigerator while the FZ-Sensor Error is showing?
It is not advisable to continue using the freezer normally while this error is active. Without a reliable temperature reading, the refrigerator control board cannot properly regulate freezer temperature, which means food in the freezer may not be kept at a safe temperature. Monitor freezer temperatures manually with a thermometer and minimize door openings until the fault is repaired.
How much does it cost to fix the FZ-Sensor Error on an LG refrigerator?
Repair cost depends on the root cause. A replacement freezer temperature sensor typically costs between $15 and $50 for the part alone. If the main PCB is at fault, parts can range from $100 to $300 or more depending on the model. Adding labor for a professional technician, total repair costs generally fall between $80 and $400.
Will resetting my LG refrigerator clear the FZ-Sensor Error?
A reset may temporarily clear the error code from the display, but it will return if the underlying hardware fault is not corrected. If the sensor is failed, the wiring is damaged, or a connector is loose, the control board will detect the same out-of-range signal and re-trigger the error after the reset. Clearing the code is only a useful step as part of a diagnostic process, not as a standalone fix.

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