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Error code reference

LG Refrigerator Error Code F-SENSOR

Freezer compartment sensor error

LG codesLG refrigerator codes

Freezer compartment sensor error: electric wire cut, short-circuit, contact failure, or sensor housing missing; displayed when sensor temperature is not lower than 122°F nor higher than -58°F.

First step from the service manual

Check the voltage between Main PCB CN 30 No. 3 ↔ 7 to see if it is 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 F-SENSOR means on a LG refrigerator

The F-SENSOR error code on an LG refrigerator indicates a fault in the freezer compartment temperature sensor circuit. This sensor is a thermistor, a resistive component whose resistance changes predictably with temperature. The control system monitors the voltage signal produced by the sensor circuit to determine the freezer temperature. When the sensed temperature falls outside the valid operating window, specifically when the reading is not lower than 122°F (50°C) and not higher than -58°F (-50°C), the main PCB flags the fault and displays F-SENSOR. This range represents the boundaries beyond which the sensor signal is considered physically implausible, pointing to a circuit fault rather than an actual temperature extreme.

The four primary causes the control system cannot distinguish between on its own are an open circuit (cut wire), a short circuit, a poor contact at a connector, or a missing sensor housing. A cut wire or open circuit drives the sensor voltage to the supply rail, while a short circuit pulls it toward ground. Either condition pushes the sensed value outside the valid range. A corroded or loose connector produces intermittent resistance that mimics these faults. A missing or improperly seated sensor housing can cause the thermistor to read ambient air instead of the freezer compartment, also producing an out-of-range value.

The first diagnostic step is to measure the voltage between pins No. 3 and No. 7 on connector CN 30 at the main PCB. A healthy sensor circuit will read between 1.0V and 4.5V depending on the current freezer temperature. A reading at or near 0V indicates a short circuit or grounded wire, while a reading near 5V indicates an open circuit or disconnected sensor. If the voltage is within range, the fault is intermittent and connector inspection is the next priority. If out of range, trace the wiring harness from CN 30 back to the sensor to isolate whether the fault is in the harness, connector, or sensor itself.

Source: manufacturer service documentation.

Common causes of F-SENSOR

  1. 01

    Faulty or failed freezer thermistor

    Part replacement

    The thermistor itself can fail open or short internally, producing a voltage at CN 30 outside the 1.0V to 4.5V operating range. This is the most common hardware failure and requires sensor replacement.

  2. 02

    Loose or corroded connector at CN 30

    Wiring / connection

    Poor contact at the CN 30 connector on the main PCB introduces variable resistance that can push the sensor reading out of the valid window. Inspect and reseat the connector, checking for corrosion or bent pins.

  3. 03

    Cut or damaged wiring harness

    Part replacement

    A wire break anywhere between the main PCB and the sensor creates an open circuit, driving the voltage reading to the supply rail. Inspect the harness routing through the freezer compartment for pinched, chafed, or cut sections.

  4. 04

    Short circuit in the sensor wiring

    Part replacement

    If the sensor wires contact each other or a ground point, the signal voltage collapses toward 0V and triggers the error. Look for areas where insulation may have worn through, particularly near door hinges or wire retainer clips.

  5. 05

    Missing or improperly seated sensor housing

    Wiring / connection

    If the sensor is not clipped into its housing or the housing is absent, the thermistor reads ambient air rather than the controlled freezer environment, which can produce readings outside the valid range. Verify the sensor is properly seated in its mounting location.

See the test procedure for each cause

Frequently asked questions about F-SENSOR

What does F-SENSOR mean on a LG refrigerator?
F-SENSOR on an LG refrigerator indicates an error in the freezer compartment temperature sensor circuit. The code is triggered when the sensor reports a temperature that is not lower than 122°F or not higher than -58°F, values that fall outside any physically realistic operating range. This points to a circuit-level fault such as a cut wire, short circuit, loose connector, or a missing sensor housing rather than an actual temperature problem in the freezer.
Can I fix the F-SENSOR error myself?
Some causes of F-SENSOR are DIY-friendly. Inspecting and reseating the connector at CN 30 on the main PCB and checking that the sensor is properly mounted in its housing require no special tools. If those steps do not resolve the code, diagnosing the wiring harness and testing sensor resistance requires a multimeter and comfort working inside the appliance. Replacing the main PCB is a more advanced repair and may benefit from professional service.
Is it safe to keep using my refrigerator while the F-SENSOR code is active?
It is not advisable to rely on the freezer while F-SENSOR is active. Without a valid temperature reading, the control board cannot regulate the freezer temperature accurately, which risks food safety. Check the freezer temperature with a separate thermometer if you need to assess whether food is still safe while you arrange for the repair.
How much does it cost to repair the F-SENSOR error on an LG refrigerator?
Repair costs vary depending on the root cause. A replacement freezer thermistor is generally an inexpensive part, typically in the range of $15 to $50, and the repair is straightforward if the wiring is intact. If the wiring harness needs replacement or the main PCB is at fault, parts and labor combined can range from $150 to $400 or more depending on the model and service rates in your area.
Will resetting the refrigerator clear the F-SENSOR code?
A power reset may temporarily clear the F-SENSOR code, but it will return as soon as the control board checks the sensor circuit again and finds the reading out of range. The underlying fault, whether a failed sensor, damaged wire, or bad connector, must be corrected before the code clears permanently. Use a reset only as a way to confirm the fault is still present after making a repair, not as a standalone fix.

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