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Error code reference

LG Refrigerator Error Code F-SEN

Freezer sensor failure detected by self-diagnosis; display blinks repeatedly at the troubled sensor location.

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Freezer sensor failure detected by self-diagnosis; display blinks repeatedly at the troubled sensor location.

First step from the service manual

Check resistance at CN30 No.3 ↔ No.7; 0Ω indicates short failure, ∞Ω indicates open failure.

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

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What F-SEN means on a LG refrigerator

The F-SEN error code on an LG refrigerator indicates that the unit's self-diagnostic system has detected a failure in the freezer temperature sensor (thermistor). The display will blink repeatedly at the location associated with the troubled sensor, alerting the technician to where the fault has been detected. This sensor is responsible for providing continuous temperature readings to the control board, which uses that data to regulate compressor cycling and maintain the correct freezer temperature.

Diagnosing the F-SEN code begins at connector CN30, specifically between pins No.3 and No.7. A resistance reading of 0 ohms across those pins confirms a short circuit failure, meaning the sensor circuit has an unintended low-resistance path, often caused by damaged or pinched wiring. A reading of infinite ohms (open circuit) indicates a break in the circuit, which is typically caused by a failed thermistor, a broken wire, or a loose/corroded connector terminal.

The freezer thermistor is a negative temperature coefficient (NTC) resistor, meaning its resistance decreases as temperature rises. When the control board receives a signal outside the expected resistance range, or no signal at all, it flags the F-SEN fault and may reduce or suspend normal cooling operation to prevent damage. Addressing this code promptly is important, as an uncorrected sensor fault can lead to temperature regulation problems and potential food spoilage.

Source: manufacturer service documentation.

Common causes of F-SEN

  1. 01

    Failed Freezer Thermistor

    Part replacement

    The thermistor itself has failed internally, producing either an open circuit (infinite resistance) or a short (zero resistance) at CN30 No.3 to No.7. This is the most frequent cause and requires replacing the sensor.

  2. 02

    Broken or Damaged Wiring

    Part replacement

    The wiring harness connecting the freezer sensor to the control board may have a break or cut, resulting in an open circuit reading. Inspect the wire run for visible damage, pinching, or brittleness from prolonged cold exposure.

  3. 03

    Loose or Corroded Connector at CN30

    Wiring / connection

    A loose connection or corrosion at the CN30 connector can interrupt the sensor signal and trigger the F-SEN code. Check that pins No.3 and No.7 are fully seated and free of oxidation or moisture damage.

  4. 04

    Shorted Wiring Harness

    Part replacement

    A pinched or chafed wire in the sensor harness can create an unintended low-resistance path, showing 0 ohms at the CN30 test points. Trace the harness along its full route to locate any contact points with sharp edges or panels.

  5. 05

    Control Board Fault

    Part replacement

    In rare cases, the main control board may misread or fail to process the sensor signal correctly even when the thermistor and wiring test within normal parameters. This should only be considered after the sensor and harness have been confirmed good.

See the test procedure for each cause

Frequently asked questions about F-SEN

What does F-SEN mean on a LG refrigerator?
F-SEN indicates that the LG refrigerator's self-diagnostic system has detected a failure in the freezer temperature sensor. The display will blink at the location of the troubled sensor. The fault can be either a short circuit (0 ohms) or an open circuit (infinite ohms), measured at connector CN30 between pins No.3 and No.7. This sensor is critical for regulating freezer temperature, so the issue should be addressed promptly.
Can I fix the F-SEN error code myself?
A knowledgeable DIYer can attempt to diagnose the F-SEN code by checking the wiring and connector at CN30 for visible damage, corrosion, or loose pins. Measuring resistance between CN30 No.3 and No.7 with a multimeter will confirm whether the sensor is shorted or open. Replacing the freezer thermistor is a moderately straightforward repair, but if the control board is suspected, professional service is recommended.
Is it safe to keep using my refrigerator when the F-SEN code is showing?
Continuing to run the refrigerator with an active F-SEN code is not recommended. Without accurate freezer temperature data, the control board cannot reliably regulate cooling cycles, which may result in the freezer running too warm or not at all. This puts frozen food at risk of spoilage. Addressing the fault as soon as possible is the safest approach.
How much does it cost to repair the F-SEN error on an LG refrigerator?
If only the freezer thermistor needs replacement, parts and labor costs typically range from around $100 to $250 depending on the specific model and service rates in your area. If the wiring harness requires repair or replacement, costs may be similar or slightly higher. A control board replacement, if needed, is generally the most expensive outcome and can range from $200 to $500 or more.
Will resetting my LG refrigerator clear the F-SEN error code?
A power reset may temporarily clear the F-SEN code from the display, but it will return if the underlying sensor fault is still present. The self-diagnostic system will re-detect the failure once the refrigerator restarts its monitoring cycle. A permanent fix requires identifying and correcting the root cause, whether that is a failed thermistor, damaged wiring, or a faulty connection at CN30.

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