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Error code reference

LG Oven Error Code F-8

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

LG codesLG oven codes

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

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What F-8 means on a LG oven

The F-8 error code on an LG oven indicates that the upper temperature probe thermistor has remained in a shorted condition for more than one minute after a cook cycle begins. A thermistor is a resistive temperature sensor whose resistance changes predictably with temperature. When the thermistor shorts internally or through its wiring, the resistance drops abnormally low, causing the oven's control board to receive a temperature signal that does not correspond to real oven conditions. The control board monitors this signal continuously, and if the shorted state persists beyond the one-minute threshold, it triggers the F-8 fault and halts operation to prevent unsafe temperature conditions.

The upper temperature probe specifically monitors the heat level in the upper oven cavity, which is critical for accurate baking and broiling. A shorted thermistor can result from physical damage to the probe itself, degraded insulation on the wiring harness, moisture intrusion, or a pinched wire creating a direct low-resistance path between the signal leads. In some cases, corrosion at the connector terminals between the probe and the control board can also create an intermittent or sustained short condition.

Diagnosing this fault requires inspecting the upper temperature probe and its associated wiring harness for visible damage, then measuring the probe's resistance with a multimeter to confirm whether it falls within the expected range for a known ambient temperature. A shorted probe will typically read near zero ohms or well below the normal resistance curve. If the wiring and connectors check out, the control board should also be evaluated, as a failed input circuit on the board can mimic a shorted probe condition.

Source: manufacturer service documentation.

Common causes of F-8

  1. 01

    Failed upper temperature probe (thermistor)

    Part replacement

    The probe itself has developed an internal short, causing it to read near zero resistance regardless of oven temperature. Testing the probe with a multimeter will show abnormally low resistance compared to expected values at room temperature.

  2. 02

    Damaged or pinched wiring harness

    Part replacement

    The wires connecting the upper probe to the control board may be pinched, melted, or frayed, creating a short between the signal conductors. Visually inspect the harness along its full length for burn marks, abrasion, or areas where it contacts sharp metal edges.

  3. 03

    Corroded or contaminated connector terminals

    Wiring / connection

    Moisture, grease, or oxidation at the connector between the probe wiring and the control board can cause an abnormal low-resistance reading. Inspect the connector pins for corrosion or debris and clean or replace the connector as needed.

  4. 04

    Moisture intrusion into the probe or harness

    Wiring / connection

    Water from cleaning or steam during cooking can enter the probe housing or wiring, creating a temporary or sustained short. Allow the oven to dry completely and retest before replacing components.

  5. 05

    Faulty oven control board

    Part replacement

    If the probe and wiring both test within normal resistance parameters, the thermistor input circuit on the control board may have failed and is incorrectly reading a short condition. Board replacement is typically the last step after all other components are ruled out.

See the test procedure for each cause

Frequently asked questions about F-8

What does F-8 mean on a LG oven?
The F-8 code means the upper oven temperature probe thermistor has been detected in a shorted state for more than one minute after a cook cycle starts. The oven control board monitors the resistance signal from the upper probe continuously, and when the signal indicates a short rather than a valid temperature reading, the oven shuts down and displays this fault. The most common causes are a failed probe, damaged wiring, or corroded connectors.
Can I fix the F-8 error on my LG oven myself?
Replacing an upper temperature probe is a repair many experienced DIYers can handle, as the probe typically mounts with one or two screws inside the oven cavity and connects via a wiring harness. However, inspecting and repairing the wiring harness or replacing the control board requires more comfort with electrical diagnostics and disassembly. Always disconnect power to the oven at the breaker before performing any internal inspection or repair.
Is it safe to use my LG oven when F-8 is displayed?
No, you should not use the oven while F-8 is active. The fault indicates the control system cannot accurately monitor the upper oven temperature, which means the oven could overheat without the control board detecting it. Continuing to operate the oven under these conditions poses a risk of overheating, potential food safety issues, and possible damage to the appliance.
How much does it cost to repair an LG oven F-8 error?
If the upper temperature probe is the failed component, replacement probes typically cost in the range of $20 to $60 for the part, with professional labor adding $75 to $150 depending on your area. If the control board is the root cause, board replacement parts alone can range from $100 to $300 or more, making that a more expensive repair. Getting a diagnostic call from a technician first can help confirm which component has actually failed before committing to parts.
Will resetting my LG oven clear the F-8 error?
Resetting the oven by turning off the breaker for a few minutes may temporarily clear the F-8 code, but the fault will return once a cook cycle starts if the underlying problem has not been resolved. Because the code triggers only after the shorted condition persists for over one minute into a cook cycle, a reset alone does not fix the failed probe, damaged wiring, or other root cause. A proper repair to the temperature probe or wiring is required to resolve the fault permanently.

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