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Error code reference

LG Freezer Error Code 1

Freezer sensor (F-SENSOR) open or short circuit

LG codesLG freezer codes

Freezer sensor (F-SENSOR) open or short circuit - sensor pickup temperature over +50°C or under -50°C.

First step from the service manual

Check voltage between MAIN PCB CN30 #4 and #8; should be within 4.5V~1.0V.

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

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What 1 means on a LG freezer

Error code 1 on an LG freezer indicates a fault with the freezer temperature sensor, referred to in the wiring diagram as the F-SENSOR. The control system monitors the sensor's resistance-based signal to track the internal freezer temperature. When the MAIN PCB detects a signal that would correspond to a temperature reading above +50°C or below -50°C, it flags the sensor circuit as either open (broken or disconnected) or shorted (wiring or sensor internally failed). These extreme out-of-range values fall outside normal operating parameters and indicate the sensor is not providing a usable signal rather than an actual temperature reading.

The diagnostic entry point for this fault is a voltage check at the MAIN PCB connector CN30, specifically between pins 4 and 8. Under normal operating conditions, this voltage should fall within the range of 1.0V to 4.5V, reflecting the changing resistance of the NTC thermistor as freezer temperature varies. A reading near 5V (supply rail) typically points to an open circuit condition, such as a broken sensor wire or failed sensor element. A reading near 0V suggests a short to ground somewhere in the sensor circuit.

Common causes include physical damage to the sensor harness, corrosion at connector terminals, a failed thermistor, or a damaged section of wiring routed through the freezer cabinet door hinge area. In rarer cases, a faulty MAIN PCB that cannot correctly read the sensor voltage may be responsible after the sensor and wiring have been confirmed good.

Source: manufacturer service documentation.

Common causes of 1

  1. 01

    Failed F-SENSOR thermistor

    Part replacement

    The NTC thermistor element inside the freezer sensor can fail open or short internally, causing an out-of-range voltage at CN30 pins 4 and 8. Resistance testing of the sensor at a known temperature can confirm this failure.

  2. 02

    Damaged or broken sensor wiring harness

    Part replacement

    Wiring between the sensor and the MAIN PCB can crack, break, or chafe, particularly in areas near the cabinet door hinge or freezer liner. A visual inspection of the full harness run and a continuity test of each wire can locate the break.

  3. 03

    Corroded or loose connector at CN30

    Wiring / connection

    The connector at MAIN PCB CN30 can develop corrosion or work loose over time, disrupting the sensor signal. Inspecting pins 4 and 8 for oxidation, bent pins, or a loose housing is a quick check before replacing components.

  4. 04

    Short circuit in sensor circuit wiring

    Part replacement

    Pinched or chafed wiring can create a short to ground, pulling the voltage at CN30 pins 4 and 8 below the 1.0V lower threshold. Careful inspection of the harness routing through the cabinet liner and any pinch points is needed.

  5. 05

    Faulty MAIN PCB

    Part replacement

    If the sensor and all associated wiring test correctly but the error persists, the MAIN PCB itself may have a failed input circuit on CN30. This is the least likely cause and should only be considered after the sensor and harness have been ruled out.

See the test procedure for each cause

Frequently asked questions about 1

What does 1 mean on a LG freezer?
Error code 1 on an LG freezer signals a problem with the freezer temperature sensor (F-SENSOR). The control board has detected a signal outside the valid range, corresponding to a temperature reading above +50°C or below -50°C, which indicates the sensor circuit is open or shorted. The sensor, its wiring, or the connector at MAIN PCB CN30 is the most likely source of the fault.
Can I fix error code 1 on my LG freezer myself?
A knowledgeable DIYer can perform the initial diagnostics by checking the voltage at MAIN PCB connector CN30 between pins 4 and 8, which should read between 1.0V and 4.5V under normal conditions. Inspecting and reseating the connector or replacing the F-SENSOR are tasks within reach if you are comfortable with basic appliance repair. If the wiring harness needs repair or the MAIN PCB needs replacement, professional service is recommended.
Is it safe to keep using my LG freezer when error code 1 is displayed?
Continued use is not recommended when error code 1 is active. Without a functioning temperature sensor, the control board cannot accurately regulate the freezer compartment temperature, which could result in food not being kept at a safe temperature. The freezer may over-cool or fail to maintain adequate cooling depending on how the control system responds to the fault.
How much does it cost to repair LG freezer error code 1?
If only the F-SENSOR thermistor needs replacement, parts typically cost in the range of $15 to $50 depending on the model, with professional labor adding $80 to $150 in most markets. If the wiring harness requires repair or replacement, costs can rise to the $100 to $250 range including labor. A MAIN PCB replacement is the most expensive scenario, potentially totaling $200 to $450 or more with installation.
Will resetting my LG freezer clear error code 1?
A power reset may temporarily clear the error code display, but if the underlying sensor circuit fault is still present, the code will return once the control board completes its diagnostic cycle. Error code 1 reflects an active hardware fault, not a software or communication glitch, so a lasting fix requires identifying and repairing the failed sensor, wiring, or connector.

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