LG Microwave F-2 Error Code — What It Means
The F-2 code on your LG microwave signals a problem with the thermistor, the temperature sensor used during convection cooking. LG support documentation states that F-2 indicates the thermistor is causing the temperature in the unit to be out of range. The code specifically appears when the sensor circuit is shorted or reading abnormally for more than one minute while the convection mode is active. This is a sensor or input fault, not something caused by how you’re using the microwave. If the code returns after a power reset, LG says the unit requires service.
Common Causes
- Failed or shorted thermistor The temperature sensor itself has drifted out of specification or developed an internal short circuit.
- Damaged wiring harness or connector The wiring between the thermistor and the control board is pinched, corroded, or has a loose or damaged connector pin.
- Control board sensor input issue The main control board is not interpreting the sensor signal correctly even when the thermistor and wiring test normal.
- Moisture or contamination on the sensor Water, grease, or debris on the thermistor or connector can create intermittent short-circuit conditions that mimic a hard failure.
- Intermittent connection at the thermistor plug A poor connection at the sensor harness can cause the circuit to read shorted or open unpredictably during heating cycles.
Step-by-Step Fix
- Unplug the microwave (or turn off the circuit breaker) and leave it disconnected for at least one minute to reset the control board, then restore power and check whether the F-2 code returns.
- Confirm the operating mode when the code appeared. F-2 is tied specifically to convection cooking, so note whether you were using convection heat or another function.
- Access the thermistor by removing the microwave’s outer cabinet panels according to your service manual. Locate the thermistor sensor, usually mounted in the cavity or convection duct.
- Inspect the thermistor and wiring closely for physical damage, heat discoloration, loose connectors, corroded pins, pinched wires, or moisture contamination.
- Test the thermistor with a multimeter set to ohms. Measure the resistance across the sensor leads and compare the reading to the specification table in your model’s service data. Flex the harness gently while measuring to catch intermittent faults. If the sensor reads shorted, open, or unstable, replace it.
- Check the wiring harness and connectors for continuity from the thermistor plug back to the control board. Repair or replace any damaged wiring or connectors.
- Replace the control board if the thermistor and all wiring test within specification but the F-2 code persists. The board’s sensor input circuit is likely faulty.
Parts Often Needed
| Part | Notes |
|---|---|
| LG microwave thermistor / temperature sensor | Amazon | Match to your exact model number. The sensor used in convection cooking mode. |
| Thermistor wiring harness | Amazon | If connectors or wiring between the sensor and control board are damaged or corroded. |
| LG microwave main control board | Amazon | Required if the sensor and wiring test good but the fault code remains. |
When to Call a Pro
Call a qualified appliance technician if you are not comfortable working with live electrical components or disassembling the microwave cabinet. Microwaves store high voltage in the magnetron and capacitor even when unplugged, which can be dangerous without proper discharge procedures. If you’ve replaced the thermistor and checked all wiring but the F-2 code still appears, the control board likely needs professional diagnosis and replacement. A technician has the service data, resistance charts, and board-level testing tools to pinpoint the fault quickly and safely.