LG Oven Error Code F-1

F-1 means the upper oven thermistor has been detected in an open-circuit condition for more than one minute after a cook cycle starts. The thermistor is the sensor that monitors oven cavity temperature and reports it to the control board. Because the board cannot verify safe operating temperatures without that signal, it halts the cook cycle and displays this fault code. The issue is located at connector CN04 pins 3 and 4 in the wiring circuit.

No, you should not attempt to use the oven while F-1 is active. The control board cannot monitor oven temperature without a functioning thermistor signal, which means it cannot prevent overheating. The oven will typically refuse to run a cook cycle in this condition, and operating it in a fault state could pose a safety risk.

If only the thermistor needs replacement, parts typically range from around 20 to 60 dollars depending on the specific model, making it one of the more affordable repairs. If a wiring harness is damaged, parts and labor can range from 80 to 200 dollars. Control board replacement, if required, is more expensive, often falling between 150 and 400 dollars or more including labor. Getting a diagnosis completed first will help narrow down which component is actually at fault before committing to a repair cost.

A knowledgeable DIYer can diagnose this fault by using the oven's built-in test mode 4 to check the sensor reading, then measuring thermistor resistance at CN04 pins 3 and 4 with a multimeter after powering the unit off. If the thermistor reads outside 1.09 kΩ at room temperature, replacing the sensor is a straightforward repair. Wiring harness or connector issues also fall within DIY range, but control board replacement is more involved and may be better handled by a technician.

A power reset by unplugging the oven or cycling the breaker may temporarily clear the code, but if the underlying cause is a failed thermistor, damaged wiring, or a loose connector, the F-1 error will return once you attempt to start a cook cycle and the one-minute open-circuit threshold is reached again. The fault must be repaired, not just reset.