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Error code reference

LG Range Error Code F-18

Probe thermistor is shorted for over 1 minute after cook starts during cooking.

LG codesLG range codes

Probe thermistor is shorted for over 1 minute after cook starts during cooking.

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What F-18 means on a LG range

The F-18 error code on an LG range indicates that the meat probe thermistor has been in a shorted condition continuously for more than one minute after cooking has begun. The probe thermistor is a temperature-sensing resistor built into the meat probe accessory, which plugs into a dedicated jack on the oven interior. Under normal operation, the thermistor changes resistance as food temperature rises, allowing the control board to monitor internal food temperature in real time. A short circuit in this circuit means the resistance has dropped to near zero ohms, which the control board interprets as an invalid or failed sensor reading, triggering the fault after a sustained one-minute period to filter out transient glitches.

The most common reason this fault appears is a damaged or defective meat probe. Physical damage to the probe cable, a bent or corroded connector, or internal failure of the thermistor element itself can all result in a short. The probe jack on the oven wall can also develop internal corrosion or debris bridging the contacts, creating a short even when no probe is connected. In some cases, the wiring harness running from the probe jack to the main control board can develop a short if insulation is worn or pinched.

Because the fault requires the short to persist for over one minute during active cooking, intermittent shorts may not always trigger the code immediately. Technicians should inspect the probe connector and jack carefully for moisture, food residue, or physical deformation. Testing the probe thermistor with a multimeter will reveal whether resistance is at or near zero ohms, confirming a shorted element. If the probe and jack both test normal, the wiring harness and control board input circuit should be evaluated.

Source: manufacturer service documentation.

Common causes of F-18

  1. 01

    Damaged or defective meat probe

    Part replacement

    The thermistor inside the meat probe has failed internally or the probe cable is damaged, causing a short circuit. Test the probe with a multimeter across the connector pins; a reading near zero ohms confirms a shorted thermistor.

  2. 02

    Corroded or contaminated probe jack

    Wiring / connection

    Food residue, grease, or moisture inside the probe jack on the oven wall can bridge the contacts and create a short even if the probe itself is functional. Inspect the jack visually and clean it carefully with a dry cloth or contact cleaner.

  3. 03

    Bent or corroded probe connector pins

    Part replacement

    If the metal pins on the probe plug are bent, corroded, or making unintended contact with each other, a short can result at the connection point. Inspect the probe plug closely and compare pin alignment to a known-good probe.

  4. 04

    Damaged wiring harness between probe jack and control board

    Part replacement

    The wiring between the probe receptacle and the main control board can develop a short if insulation is pinched, burned, or worn through. This requires accessing the oven interior panels to visually trace and test the harness.

  5. 05

    Faulty main control board

    Part replacement

    If the probe, jack, and harness all test correctly, the input circuit on the main control board may have failed internally and is incorrectly reading the probe circuit as shorted. This is the least common cause and should be diagnosed only after all other components are ruled out.

See the test procedure for each cause

Frequently asked questions about F-18

What does F-18 mean on a LG range?
The F-18 code on an LG range means the meat probe thermistor has been detected in a shorted state for more than one minute during active cooking. The control board monitors the resistance of the probe sensor continuously, and a near-zero resistance reading that persists triggers this fault. It points to a problem with the probe itself, the probe jack, or the wiring connected to it.
Can I fix the F-18 error myself?
In many cases, yes. Start by unplugging the meat probe from the oven jack and inspecting both the probe cable and the connector for visible damage, corrosion, or debris. If the probe appears damaged, replacing it is a straightforward repair that does not require disassembling the oven. If the jack or internal wiring is the source of the short, a technician may be needed to safely access and repair those components.
Is it safe to use my LG range while the F-18 code is showing?
You should not attempt to continue cooking with the meat probe connected while this code is active, as the control board cannot accurately monitor probe temperature. However, if you remove the meat probe entirely, standard bake and broil functions that do not rely on the probe may still operate normally. Confirm the error clears after removing the probe before using the oven.
Will resetting the range clear the F-18 error code?
Resetting the range by cycling the power may temporarily clear the display, but the code will return if the underlying short in the probe circuit is still present once cooking begins again. A lasting fix requires identifying and correcting the cause, whether that means replacing the probe, cleaning the jack, or repairing damaged wiring.
How much does it cost to repair an F-18 error on an LG range?
If only the meat probe needs replacement, the cost is typically in the range of $20 to $60 for the part, making it one of the more affordable oven repairs. If the probe jack or wiring harness is damaged, parts and labor can bring the total to somewhere between $100 and $250 depending on the extent of the repair. A failed control board is the most expensive scenario, with costs potentially ranging from $200 to $400 or more including labor.

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