LG Microwave F2 Error Code — What It Means
The F2 error code on an LG microwave indicates a thermistor problem that has caused the unit temperature to be out of the expected range. The thermistor is a temperature sensor that monitors cavity and component heat during operation. When the control board reads a signal outside normal limits, it throws F2 and stops heating to protect the unit. LG’s official guidance states this error requires service, as the fault involves internal sensor circuits that are not user-adjustable.
Common Causes
- Failed thermistor The temperature sensor itself has drifted out of tolerance, reads open, or shorted, sending invalid resistance values to the control board.
- Loose or corroded sensor connector The harness plug at the thermistor or control board has backed out, corroded, or developed a high-resistance connection that mimics sensor failure.
- Damaged sensor wiring harness Wires between the thermistor and control board are pinched, cut, or have insulation breakdown, causing intermittent or open circuits.
- Control board input fault The thermistor and wiring test good, but the main control board is misreading the sensor signal due to a component failure on the input circuit.
Step-by-Step Fix
- Disconnect power at the breaker or unplug the microwave and wait two minutes for capacitors to discharge before opening any panel.
- Remove the outer cabinet or access panel to expose the cavity and main control board, following your model’s disassembly sequence.
- Locate the thermistor (a small sensor with two wires, usually clipped or fastened near the magnetron or cavity wall) and inspect the connector, terminals, and harness for damage, corrosion, or loose fit.
- Disconnect the thermistor plug and measure the sensor resistance at room temperature using a multimeter, then compare the reading to your model’s service data or consult a technician if you do not have the specification.
- If the sensor reads open, shorted, or far out of range, replace the thermistor. If the sensor measures correctly, check continuity through the harness to the control board and inspect the board connector.
- Replace the identified defective component (thermistor, harness connector, or main control board if the sensor circuit is valid but the fault persists), reassemble the unit, and restore power.
- Run a short heat cycle and verify the microwave operates normally with no F2 code and proper temperature sensing throughout the cycle.
Parts Often Needed
| Part | Notes |
|---|---|
| LG microwave thermistor / temperature sensor | Amazon | Match the part number to your exact microwave model, as sensor specs vary by series. |
| Sensor wiring harness and connectors | Amazon | Order if pins are corroded or the harness is damaged beyond field repair. |
| LG microwave main control board | Amazon | Required only when the thermistor and harness test good but F2 persists, indicating a board-side input fault. |
When to Call a Pro
LG explicitly states that F2 requires service. The repair involves working inside a microwave with high-voltage capacitors and magnetron circuits that retain lethal charge even after unplugging. If you are not trained in microwave safety, discharge procedures, and sensor diagnostics, or if you lack the service manual resistance specifications for your model’s thermistor, call a qualified appliance technician. Also call if you replace the sensor and harness but the fault returns, as the problem is then on the control board or a secondary thermal-protection circuit that requires schematic-level troubleshooting.