LG Oven Error Code F4

LG Oven F4 Error — What It Means

The LG oven F4 error code typically signals a problem with the oven’s temperature sensing or temperature regulation system. In many LG ranges and wall ovens, F4 is triggered when the control board detects an open, shorted, or out-of-range temperature sensor (thermistor/RTD) or when wiring/connectors to that sensor are faulty. When the oven cannot read or control temperature correctly it can lead to uneven cooking, longer cook times, oven cycling (turning on and off repeatedly), or a full oven shut-down as a safety precaution. Left unresolved, the condition can create safety risks (overheating or failure to reach safe cooking temperatures), poor baking/roasting results, and repeated lockouts that interrupt use.

Common Causes

• Faulty oven temperature sensor (thermistor or RTD) — open or shorted element.
• Damaged or loose wiring harness to the sensor or control board.
• Corroded or broken terminal/connectors at the sensor or main board.
• Failed or intermittent main control board (PCB) that misreads the sensor signal.
• High-heat damage from spills, burned food, or physical impact to the sensor.
• Software/glitch requiring a power reset or control board firmware reinitialization.
• Incorrect sensor installation after a repair or replacement.

Troubleshooting Steps

1. Safety first: disconnect power to the oven at the circuit breaker or unplug the range before inspecting any components.
2. Power reset: restore power after 60 seconds to clear temporary errors — note if F4 returns during the next heat cycle.
3. Visual inspection: open the oven and check the sensor (usually a probe protruding from the oven wall) for visible damage, bends, or loose mounting screws.
   • Inspect wiring behind the back panel for chafing, burn marks, or disconnected plugs.
4. Check connectors: remove and reseat the sensor connector at the terminal block or control board to ensure a solid connection.
5. Measure the sensor: with power off, use a multimeter set to the resistance (ohms) range to check continuity of the sensor. Compare the reading to the OEM service manual or expected values — a completely open (infinite) or shorted (near 0 Ω) sensor indicates replacement.
   • If you don’t have specs: a healthy oven temperature sensor typically shows a stable resistance (not infinite) at room temperature; dramatic or unstable readings suggest failure.
6. Test wiring: if the sensor reads correctly, test continuity from the sensor connector to the control board to rule out broken wiring.
7. Swap or replace the sensor: if the sensor or wiring is defective, replace the sensor with an OEM or equivalent part and retest.
8. Inspect the control board: if sensor and wiring test good but F4 persists, the main control board may be failing — look for burned components or bulging capacitors. Diagnosis or replacement by a technician is recommended.
9. Run a diagnostic mode (if available): some LG ovens have built-in diagnostics to read sensor values and log errors; consult your manual for steps to access diagnostics.
10. Call a professional: if you are not comfortable with electrical testing or the error remains after replacing obvious parts, contact an authorized LG technician for safe diagnosis and repair.

Maintenance / Prevention Tips

• Keep the oven interior clean — baked-on spills can overheat near the sensor and cause damage.
• Avoid spraying cleaning chemicals directly on the sensor or control panel.
• Use gentle, non-abrasive cleaners and soft cloths when cleaning near sensitive components.
• Inspect the sensor and wiring every 6–12 months for signs of wear or damage.
• Do not bang or strike the oven interior — physical shock can bend or break the sensing probe.
• Use properly sized bakeware to prevent excessive heat concentration near one wall where the sensor is located.
• Make sure replacement sensors are OEM-compatible and installed exactly as the manufacturer directs.
• Securely fasten the sensor mounting screws after any service to keep the probe in correct position.
• Keep the oven door gasket in good condition to prevent heat loss and uneven temperature readings.
• Schedule periodic professional maintenance for high-use ovens (restaurants or frequent bakers).
• When using self-clean cycles, remove racks or cover components that the manual recommends to avoid heat damage.
• Avoid overloading the oven which can trap heat near sensors and reduce airflow.
• Address any small error codes promptly — don’t let intermittent faults become persistent failures.
• Use surge protection for kitchen circuits where frequent brownouts or surges occur.
• Keep the area behind and beneath the oven free of dust and debris that can cause heating issues around control electronics.

FAQs

Conclusion / Safety Notice

When your LG oven displays the F4 code, treat it as a sign that temperature sensing or regulation needs attention. Always cut power before inspecting wiring or components, and avoid continued use that could risk food safety or further damage. If basic troubleshooting (power reset, reseating connectors, replacing a clearly failed sensor) does not clear the error, stop attempts at repair and contact an authorized LG service provider or a certified appliance technician.

For safe and lasting repairs, consider professional diagnosis if you lack the tools or experience to test electrical components. Prompt professional service helps ensure correct parts are used and that the oven is safe to operate.