LG oven F3 error is a common fault code that typically points to a temperature sensing or communication problem inside the oven. When the control system detects a reading from the oven temperature sensor (NTC thermistor) that is out of expected range — open, shorted, or inconsistent — it will display F3 and may stop normal heating or put the oven into a fault state. The practical impacts for users include inaccurate cooking temperatures, longer or uneven cook times, oven not heating at all, unexpected shutoffs, and in some cases a potential safety concern if the appliance cannot reliably monitor its temperature.
Common causes
- Faulty oven temperature sensor (NTC thermistor) — open, shorted, or drifting out of spec
- Loose, corroded, or damaged wiring harness or connector between sensor and control board
- Damaged or failing main control board (electronic control / PCB) misreading the sensor
- Burnt or loose terminal connections where the sensor plugs into the control board
- Heat damage to the sensor or harness from heavy use, spills, or physical impact
- High-limit thermostat or thermal fuse triggering or failing (less common but possible)
- Software/firmware glitch (rare) or incorrect diagnostics from the control board
Troubleshooting steps
- Power safety first: Turn the oven off and disconnect power at the circuit breaker before inspecting or attempting any repairs.
- Reset and re-test: Turn power off for 60 seconds, restore power and see if F3 returns. Temporary resets can clear intermittent faults.
- Visual inspection: Open the oven and inspect the temperature sensor (usually on the back wall), wiring and plug for obvious damage, burn marks, pin corrosion or loose connections.
- Access the sensor: Remove the screws securing the sensor probe to the oven cavity and gently pull it out to expose the connector (refer to your model’s service manual).
- Measure sensor resistance: With the sensor disconnected and cold (room temperature), measure resistance with a multimeter. Typical NTC oven sensors read roughly 1,000–1,200 ohms at ~25°C (check your model’s spec). An open circuit (infinite) or near-zero indicates a bad sensor.
- Check wiring continuity: Test continuity from the sensor connector to the control board connector. Repair or replace any damaged wires or connectors.
- Swap or test the sensor: If you have a known-good sensor or can temporarily replace it, that’s a quick way to confirm the diagnosis.
- Inspect control board: If the sensor and harness test good, inspect the control board for burnt components, swollen capacitors, or damaged terminals. Boards can fail and misread sensors.
- Replace the failed component: Replace the sensor, harness, or control board as indicated by your tests. Use OEM parts where possible to ensure accuracy and longevity.
- Final test: Reassemble, restore power, and run a bake cycle or self-test per the owner’s manual to verify the F3 code no longer appears and the oven reaches set temperatures.