LG Oven F5 Error Code — What It Means
The F5 error code on LG ranges and ovens indicates a lower oven thermistor error. The control board is seeing the temperature sensor signal from the lower oven as out of range or otherwise invalid, so it stops normal operation to prevent unsafe heating. LG classifies this fault as a thermistor error, pointing to the temperature-sensing circuit rather than the heating element itself.
In practical terms, the thermistor (a temperature-dependent resistor that tells the control how hot the oven is) has either failed, become disconnected, or is sending a reading the board cannot interpret. The fault can also appear if the wiring or connector between the sensor and the control board is loose, corroded, or damaged. Less commonly, a control board input fault can trigger F5 even when the sensor circuit is intact.
Common Causes
- Failed lower oven thermistor The temperature sensor has failed open, shorted, or drifted out of specification and no longer provides a valid resistance signal to the control board.
- Loose or damaged sensor wiring The harness, connector, or terminals between the thermistor and the control board are corroded, loose, broken, or showing heat damage.
- Intermittent sensor connection The plug or crimp connection at the sensor or control board is making and breaking contact, causing the code to appear and disappear.
- Control board input circuit fault The sensor and wiring test correctly, but the control board input circuitry is misinterpreting or not reading the thermistor signal.
Step-by-Step Fix
- Press CLEAR/OFF and turn off the circuit breaker for 30 seconds, then restore power and retry the oven function to see if the code clears.
- Access the lower oven cavity by removing racks, the lower panel, or rear access cover as required by your model to reach the thermistor probe and wiring.
- Inspect the thermistor probe and harness for visible damage, corrosion, loose connectors, burnt insulation, or melted terminals at both the sensor and control board ends.
- Disconnect the thermistor from the oven control board and measure its resistance with a multimeter at room temperature, then compare to the manufacturer specification for your model number (consult your service manual or model-specific resistance table).
- Check wiring continuity by testing each wire from the thermistor plug to the control board plug to confirm there are no breaks, high resistance, or shorts to ground.
- Replace the thermistor if it reads open, shorted, or out of tolerance, or replace the harness if you find a wiring fault.
- Replace the oven control board if the sensor and wiring both test good but the F5 code returns after power reset and reinstallation.
Parts Often Needed
| Part | Notes |
|---|---|
| LG lower oven thermistor / temperature sensor | Amazon | Match the part number to your specific LG range model number, usually found on the data plate inside the oven door or on the back panel. |
| Oven sensor wiring harness | Amazon | Order if you find broken, burnt, or corroded wiring that cannot be repaired with splice or terminal replacement. |
| LG oven control board (main ERC) | Amazon | Required only if sensor and wiring verify good but the F5 fault persists after reset and reinstallation. |
When to Call a Pro
Call a qualified appliance technician if you are not comfortable working with electrical components or removing oven panels, if the error returns after replacing the thermistor and you lack the tools to verify control board input circuits, or if your oven is still under warranty. A pro can perform model-specific resistance checks, measure board input voltage, and confirm the root cause before ordering expensive control parts. If you have a double oven and the upper oven also shows faults, or if you see arcing, smoke, or repeated breaker trips, shut off power at the panel and call for service immediately.