Door latch switch
Common interlock fault part on appliance no-start errors.
LG ovens and ranges (including those with ThinQ) are highly sophisticated, but they use sensitive electronic sensors to monitor temperature and airflow. When your oven stops and shows a code like F3 or F9, it’s usually because it’s detecting a temperature that’s out of range or a heating element that’s taking too long to reach the set temperature.
Most LG oven errors can be resolved with a power reset or by checking the temperature sensor.
What This Error Means
LG ovens use an “F” followed by a number to indicate specific component failures.
- F3: This is the “Open or Shorted Sensor” error. The oven’s “thermometer” (RTD) is broken.
- F9: The oven is not heating or is heating too slowly.
- F5: Communication failure between the main board and the relay board.
- CL: This isn’t an error! It’s Child Lock. Just hold the “Clock” or “Clear/Off” button for 3 seconds to disable it.
Common LG Oven Error Codes
| Code | Meaning | Severity | Fix |
|---|---|---|---|
| F3 | Temperature Sensor (RTD) fault | Moderate | Replace sensor probe |
| F9 | Heating failure | Moderate | Check element / Reset |
| F5 | Control board communication | High | Power cycle / Reset |
| F1 | Keypad / Touch panel error | Low | Clean panel or reset |
| CL | Child Lock is ON | Low | Hold button for 3 seconds |
Step-by-Step Fix
1. Resolving the “F3” Sensor Error
This is the most common hardware failure in LG ovens. The sensor probe has either burnt out or its wiring has melted.
- Unplug the oven or turn off the breaker.
- Open the oven door. Locate the Temperature Sensor (a thin metal rod) at the top back corner.
- It is usually held in by two Phillips screws. Remove them and pull the sensor forward to reveal the connector.
- Unplug the sensor and replace it with a new one. This is a 5-minute fix that costs about $20.
2. Fixing the “F9” Heating Error
If your oven turns on but never gets hot:
- Power Reset: Turn off the circuit breaker for 10 minutes. Sometimes the relay board gets stuck and needs a full discharge.
- Check the Element: If you have an electric oven, look at the bottom heating element. Does it glow red? If there are any blisters, cracks, or dark spots on the element, it has “blown” and needs to be replaced.
- Check the Igniter: If you have a gas oven, look for a glow in the bottom. If the igniter glows for minutes but the gas never catches, the igniter is too weak and needs replacement.
3. Resolving the “F5” Communication Error
- This error often happens during a self-cleaning cycle when the oven gets extremely hot.
- Turn off the breaker and let the oven cool down for 2 hours.
- Turn the breaker back on. If the F5 code returns immediately, one of the internal control boards has been damaged by the heat and needs to be replaced.
4. Disabling “CL” (Child Lock)
- If your oven display says “CL” and no buttons work, don’t panic.
- Find the button that has a small “Lock” icon next to it (usually Clear/Off, Clock, or Settings).
- Press and hold it for 3 to 5 seconds. The “CL” will disappear and the oven will beep.
Parts You May Need
- LG Oven Temperature Sensor (RTD) Replacement
- LG Electric Bake Element (Bottom)
- LG Gas Oven Igniter
- Oven Temperature Thermometer (for Calibration)
When to Call a Professional
Ovens use 240V electricity or gas—safety is the priority.
- F7 Error: This is a door lock motor failure. If your oven door is stuck locked after a cleaning cycle, do not force it. A technician needs to manually release the latch.
- Sparking or Arcing: If you see sparks inside the oven, turn off the breaker immediately.
- Oven is over-cooking everything: If your oven is much hotter than the display says, the main control board’s relays are likely stuck in the “ON” position.