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Error code reference

LG Range Error Code F4

Main oven temperature sensor shorted

LG codesLG range codes

Main oven temperature sensor shorted - oven thermistor is shorted for over 1 minute after cook starts.

First step from the service manual

Disconnect power, check for loose oven sensor connector, measure sensor resistance (approx. 1.09k ohms at room temp).

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

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What F4 means on a LG range

The F4 error code on an LG range indicates that the main oven temperature sensor (thermistor) has developed a short circuit condition. Specifically, the control board detects a shorted signal from the oven sensor for more than one continuous minute after a cook cycle begins. The thermistor is a resistive sensor that changes resistance in proportion to temperature. At room temperature, a properly functioning sensor reads approximately 1.09k ohms. When the sensor shorts, its resistance drops far below this expected value, causing the control board to read an impossibly high temperature signal and shut down oven operation to prevent damage or a safety hazard.

The oven temperature sensor is typically located inside the oven cavity, mounted through the rear wall, with a connector that links to the main control board wiring harness. A short can occur within the sensor element itself, along the sensor wiring between the oven cavity and the control board, or at the connector junction. Heat cycling, physical damage, grease contamination, and wire insulation degradation are all known contributors to sensor failure on ranges.

Diagnosing this code requires disconnecting power to the range, inspecting the sensor connector for looseness or corrosion, and measuring the sensor resistance with a multimeter. A reading significantly below 1.09k ohms at room temperature confirms a shorted sensor. If the sensor resistance is within range, the wiring harness and control board connections should be inspected for damage or a short to ground before replacing components.

Source: manufacturer service documentation.

Common causes of F4

  1. 01

    Failed oven temperature sensor

    Part replacement

    The thermistor element inside the sensor probe has internally shorted, dropping resistance well below the expected 1.09k ohms at room temperature. Confirm by measuring resistance across the sensor terminals with a multimeter after disconnecting power.

  2. 02

    Loose or corroded sensor connector

    Wiring / connection

    The connector joining the sensor to the wiring harness can loosen over time or accumulate corrosion, causing a low-resistance short between terminals. Inspect the connector visually and reseat it firmly before condemning the sensor.

  3. 03

    Damaged sensor wiring harness

    Part replacement

    The wires running from the oven sensor through the range cavity to the control board can develop damaged insulation from heat exposure, allowing conductors to short against the metal chassis or each other. Trace the harness visually for pinched, melted, or frayed sections.

  4. 04

    Grease or moisture contamination at the sensor connector

    Wiring / connection

    Accumulated grease or moisture bridging the sensor connector pins can create a low-resistance path that mimics a shorted sensor. Cleaning the connector with electrical contact cleaner and allowing it to dry fully may resolve this condition.

  5. 05

    Faulty main control board

    Part replacement

    If the sensor resistance measures correctly at approximately 1.09k ohms at room temperature and the wiring harness shows no damage, the control board's sensor input circuit may have failed. This is the least common cause and should only be considered after other components are ruled out.

See the test procedure for each cause

Frequently asked questions about F4

What does F4 mean on a LG range?
The F4 code on an LG range means the main oven temperature sensor has been detected in a shorted condition for more than one minute after a cook cycle starts. The sensor, also called a thermistor, is a probe inside the oven cavity that monitors temperature and should read approximately 1.09k ohms at room temperature. When it shorts, the resistance drops abnormally and the control board disables the oven. The fault must be resolved before normal cooking operation can resume.
Can I fix the F4 error on my LG range myself?
Many homeowners and DIYers can address this repair with basic tools. Start by disconnecting power, then check the sensor connector at the back of the oven cavity for looseness or corrosion and reseat it. Use a multimeter to measure sensor resistance, comparing your reading to the expected value of approximately 1.09k ohms at room temperature. If the sensor reads significantly low, replacing the oven temperature sensor is a straightforward repair that typically involves removing one or two mounting screws and a wiring connector.
Is it safe to use my LG range while the F4 code is showing?
The oven portion of the range should not be used while the F4 error is active. The code indicates the temperature sensor is not providing reliable readings, which means the oven cannot accurately regulate heat. Continuing to operate the oven under these conditions could result in overheating. Surface burners on a gas or electric range may still function normally, but oven use should be avoided until the fault is resolved.
How much does it cost to fix the F4 error on an LG range?
If the repair only requires a new oven temperature sensor, parts typically cost in the range of $20 to $60 depending on the specific model. If a professional technician is needed for diagnosis and installation, total repair costs including labor generally fall between $100 and $250. In less common cases where the main control board is at fault, parts alone can range from $150 to $350 or more, making professional diagnosis especially worthwhile before purchasing a board.
Will resetting my LG range clear the F4 error code?
Disconnecting power to the range for a few minutes and restoring it may temporarily clear the F4 code, but the error will return once a cook cycle starts if the underlying sensor fault has not been corrected. The control board triggers F4 after detecting a shorted sensor for over one minute during cooking, so the code is tied to an active hardware condition rather than a stored memory glitch. A reset is useful for confirming whether a connector seating issue resolved the problem, but it is not a permanent fix on its own.

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