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LG F1

LG Oven Error F1: Upper Oven Thermistor Error — Open Circuit

Clear meaning, realistic next steps, and safe guidance without turning the page into a long repair manual.

What it means

The upper oven temperature sensor (thermistor) is reading an open circuit — its resistance is outside the valid range, meaning the oven cannot monitor temperature in the upper cavity.

Severity

High - stop using the LG oven until the cause is understood or professional help is arranged.

Can you fix it yourself?

Partial — start with DIY steps

Most likely cause

Oven thermistor has failed — element is open-circuited

Estimated time for safe first checks: 15–30 min for sensor check and replacement.

Step-by-Step DIY Fix Guide

  1. SAFETY: Turn off the oven and disconnect power at the circuit breaker.
  2. Reset by restoring power after 60 seconds and testing a short bake cycle.
  3. If F1 returns, locate the oven temperature sensor — it is a small probe, usually mounted to the back wall of the upper oven cavity with two screws.
  4. Unscrew the sensor and pull it forward. Check the wiring harness connector at the back of the sensor — disconnect and reconnect firmly.
  5. If the connector is secure and F1 persists, the thermistor itself needs replacing. It can be tested with a multimeter — at room temperature (70°F), a good LG oven thermistor reads approximately 1080–1090 ohms.
  6. If the resistance is open (infinite) or very far from 1080–1090 ohms, replace the sensor.

If the warning comes back after restart

  • If the warning returns immediately after a clean restart, the sensor or wiring path becomes more likely than a one-time glitch.
  • F1 persists after reconnecting the sensor harness and multimeter reading confirms open circuit

What This Error Means

Error F1 on your LG oven means: The upper oven temperature sensor (thermistor) is reading an open circuit — its resistance is outside the valid range, meaning the oven cannot monitor temperature in the upper cavity. The range's self-diagnostic system has detected this condition.

The most frequent cause is oven thermistor has failed — element is open-circuited (broken wire inside the sensor). Work through the causes and fix steps below in order — many LG oven errors are resolved without a service call.

Many cases of F1 can be resolved by the homeowner. The steps below cover the full DIY checks — if they do not resolve the error, a technician is needed.

Oven temperature sensor faults are among the most common LG oven errors. The sensor is a simple probe on the back wall of the oven cavity — reconnecting a loose harness connector resolves around half of all sensor fault codes. Sensor replacement is a 15-minute DIY repair when the connector check does not resolve it.

Most Likely Cause by Symptom

The LG oven may stop, pause, or refuse to complete the cycle normally.

Likely cause: Oven thermistor has failed — element is open-circuited (broken wire inside the sensor)

Check first: SAFETY: Turn off the oven and disconnect power at the circuit breaker.

The warning may return immediately because the appliance is detecting an internal fault.

Likely cause: Wiring harness connector to the thermistor has come loose or corroded at the connection point

Check first: Reset by restoring power after 60 seconds and testing a short bake cycle.

Common Causes

  • Oven thermistor has failed — element is open-circuited (broken wire inside the sensor)
  • Wiring harness connector to the thermistor has come loose or corroded at the connection point
  • Thermistor physically damaged by contact with a baking pan or oven rack during cleaning

What Not to Do

  • Do not run the oven with F1 active — without a working temperature sensor, the oven cannot regulate heat and may overheat

Model and Display Variation Notes

Model-family notes

  • LG oven display wording and code formats can vary by series.
  • If your model behaves differently, check the owner manual before trying any deeper maintenance step.

Display and panel differences

  • Panel wording can vary by series, so confirm the exact code pattern before buying parts.

Parts, Tools and Service Options

Service option

LG service visit if the warning returns after the basic checks are complete.

Manual and model check

Check your exact model and manual before ordering any LG oven parts.

Common parts

  • Oven temperature sensor/thermistor if sensor has failed ($15–$40)

This section stays service-first because the page points more strongly toward support or professional repair than a routine parts purchase.

When Not to Keep Troubleshooting

F1 persists after reconnecting the sensor harness and multimeter reading confirms open circuit

How to Prevent It Recurring

  • Do not allow baking pans to contact the temperature sensor probe on the oven back wall — use pans sized appropriately for your oven

Related Error Codes

Extra notes

  • This page is based on LG support material and stays conservative where model-specific guidance may vary.
  • The goal is to help you identify safe first checks before you move into parts, service, or model-specific manual lookup.

Source and model notes

Last reviewed: 2026-04-08

Based on: Based on LG support material and edited into consumer-safe guidance for the exact code family on this page.

View LG US Official Support

Model coverage note: LG oven code meanings can vary by series, control panel, and model family, so use this page as a safe starting point rather than a replacement for the model-specific manual.

Important: FixThisError is an independent guide, not the manufacturer. Use your model-specific manual when the panel wording or behavior differs.

Always disconnect power before inspecting appliances. If unsure, contact a licensed appliance technician.