LG Range F4 Error Code — What It Means
The F4 code on your LG electric range signals a thermistor error in the lower oven temperature sensor circuit. LG Canada documentation specifically identifies F4 as a shorted oven sensor. This is not a cooktop surface sensor issue. The fault means the control board is reading an abnormal signal from the thermistor that monitors oven cavity temperature, either because the sensor itself has failed or because wiring between the sensor and the board is damaged.
Common Causes
- Shorted oven thermistor The lower oven temperature sensor has developed an internal short to ground or between its leads, the primary cause LG lists for F4.
- Damaged or loose sensor wiring harness The connector or wiring between the thermistor and the control board is corroded, pinched, or has loose terminals that create intermittent shorts.
- Sensor connector corrosion Moisture or high heat has degraded the plug at the sensor or at the control board, causing false short readings.
- Failed control board input circuit The main control board’s thermistor input circuit has failed, though LG directs you to check the sensor and harness first.
Step-by-Step Fix
- {‘lead’: ‘Power off the range at the control panel’, ‘text’: ‘turn the unit off using the range controls, then flip the circuit breaker off for at least 30 seconds and restore power to clear the fault from memory.’}
- {‘lead’: ‘Observe whether F4 returns immediately’, ‘text’: ‘if the code reappears as soon as the range powers back on, you have a persistent sensor-circuit fault that requires physical inspection.’}
- {‘lead’: ‘Disconnect power at the breaker again’, ‘text’: ‘then remove the lower oven cavity panel or rear access cover to expose the oven thermistor and its wiring harness (location varies by model).’}
- {‘lead’: ‘Inspect the thermistor and its connector for visible damage’, ‘text’: ‘look for burn marks, pinched insulation, loose terminals, or corrosion at the sensor body and the connector plug on both the sensor and board ends.’}
- {‘lead’: ‘Disconnect the thermistor leads and measure resistance across the sensor terminals’, ‘text’: “compare your reading to the service specification for your exact LG model (consult your model’s service manual or parts table, as LG does not publish a universal value).”}
- {‘lead’: ‘Replace the lower oven thermistor if it reads shorted (near zero ohms) or open (infinite resistance)’, ‘text’: ‘if the sensor tests correctly but the code persists, inspect and replace the wiring harness or connector if damaged.’}
- {‘lead’: ‘If the sensor circuit proves good and F4 still appears’, ‘text’: “the main control board’s thermistor input has likely failed and the board requires replacement by a qualified technician.”}
Parts Often Needed
| Part | Notes |
|---|---|
| LG oven thermistor / lower oven sensor | Amazon | Match the part number to your exact LG range model (often stamped on the original sensor body or listed in your manual). |
| Oven sensor wiring harness | Amazon | Order the sensor-to-board harness if you find physical damage or melted connectors that cannot be repaired with new terminals. |
| LG range main control board / oven PCB | Amazon | Replace only after confirming the sensor and harness test within specification and the fault persists. |
When to Call a Pro
LG states that F4 requires service if a simple power reset does not clear the code. If you are uncomfortable working inside a 240-volt appliance, opening the oven cavity panels, or using a multimeter to measure thermistor resistance, call a qualified appliance technician. Licensed techs carry model-specific resistance tables, can verify control-board input circuits, and will make sure the repair meets electrical code. If your range is still under warranty, contact LG or an authorized service provider before opening any panels.