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Error code reference

LG Range Error Code F-8

Upper temp probe thermistor is shorted over 1 minute after cook starts.

LG codesLG range codes

Upper temp probe thermistor is shorted over 1 minute after cook starts.

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What F-8 means on a LG range

The F-8 error code on an LG range indicates that the upper oven temperature probe thermistor has detected a shorted condition that persists for more than one minute after the cook cycle begins. A thermistor is a resistance-based temperature sensing component whose electrical resistance changes predictably with temperature. When the thermistor shorts internally or through its wiring circuit, the resistance drops abnormally low, causing the oven control board to receive an incorrect temperature signal. The control board interprets this sustained short condition as a fault and displays the F-8 code to protect the oven from running without accurate temperature data.

The upper temp probe thermistor is located inside the upper oven cavity and connects back to the electronic control board via a two-wire harness. A short can occur within the thermistor probe itself, within the wiring harness connecting it to the control board, or at the connector terminals where the harness meets either the probe or the board. Physical damage such as pinched wiring, heat degradation of wire insulation, or moisture intrusion can all create a short-to-ground or wire-to-wire short condition in this circuit.

Because the fault must persist for over one minute after cooking starts, intermittent wiring issues that stabilize quickly may not always trigger F-8. However, a thermistor probe that has failed internally will produce a consistent short and trigger the code reliably at the start of every cook cycle. Diagnosing this fault requires measuring the resistance across the thermistor probe terminals and inspecting the harness for visible damage or compromised insulation.

Source: manufacturer service documentation.

Common causes of F-8

  1. 01

    Failed upper oven temperature probe

    Part replacement

    The thermistor probe itself can fail internally, causing its resistance to drop to near zero and creating a persistent short condition. Testing the probe with a multimeter at room temperature will reveal abnormally low or zero resistance instead of the expected value for the ambient temperature.

  2. 02

    Damaged or shorted thermistor wiring harness

    Part replacement

    The wiring between the probe and the control board can develop a short due to pinching, heat damage, or insulation breakdown. Visually inspect the harness along its entire route for melted insulation, bare wire contact points, or pinch marks.

  3. 03

    Corroded or loose connector terminals

    Wiring / connection

    The connector terminals at the probe end or the control board end of the harness can corrode or back out, causing an intermittent or sustained short. Inspect both connectors for discoloration, corrosion, or terminals that are not fully seated.

  4. 04

    Moisture or grease contamination in the circuit

    Wiring / connection

    Spillovers or steam can introduce moisture or grease into the thermistor connector, creating a conductive path between the two signal wires and simulating a short. Cleaning and thoroughly drying the connectors may resolve the fault if no other damage is present.

  5. 05

    Faulty electronic control board

    Part replacement

    If the thermistor probe and all wiring test correctly with a multimeter, the control board's thermistor input circuit may have failed internally. This is the least common cause and should only be considered after the probe and harness are confirmed good.

See the test procedure for each cause

Frequently asked questions about F-8

What does F-8 mean on a LG range?
F-8 on an LG range means the upper oven temperature probe thermistor has been detected in a shorted condition for more than one minute after a cook cycle starts. The oven control board monitors the thermistor's resistance to track oven temperature, and a short causes the resistance to read abnormally low. The oven displays F-8 and stops operation to prevent cooking without reliable temperature feedback. The most likely causes are a failed temperature probe or damaged wiring in the thermistor circuit.
Can I fix the F-8 error on my LG range myself?
A knowledgeable DIYer can diagnose and resolve F-8 by testing the upper oven temperature probe with a multimeter and inspecting the wiring harness for visible damage. If the probe tests as shorted, it can typically be replaced by removing a couple of mounting screws inside the oven cavity and unplugging the harness connector. However, if the control board is involved, or if working around oven wiring is unfamiliar territory, a qualified appliance technician is the safer option.
Is it safe to use my LG range while the F-8 code is showing?
It is not advisable to continue using the upper oven while F-8 is active. The error indicates the oven has no reliable temperature data from its upper probe, meaning the control board cannot properly regulate heat. Operating the oven in this condition risks overheating. Address the fault before using the upper oven again.
Will resetting my LG range clear the F-8 error code?
Resetting the range by cycling the power at the breaker may temporarily clear the F-8 display, but the code will return as soon as the oven runs for more than one minute if the underlying fault is still present. The shorted thermistor condition is hardware-based, so a reset alone will not resolve the problem. A proper repair requires diagnosing and correcting the fault in the thermistor probe or its wiring circuit.
How much does it cost to repair an F-8 error on a LG range?
If the repair requires only a new upper oven temperature probe, parts typically range from around 20 dollars to 60 dollars depending on the specific model, and the repair is straightforward. If wiring harness repair or control board replacement is needed, total repair costs including labor can range from roughly 150 dollars to 350 dollars or more. Getting a diagnostic from a certified technician first can help narrow down exactly which component needs to be replaced before committing to parts costs.

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