LG Microwave Error Code E-21

E-21 on an LG microwave is a Temperature Sensor Open Error. It occurs when the control board reads a temperature sensor value above 250, indicating the sensor circuit is open or the sensor has failed. The microwave enters cancel mode automatically when this error is detected, stopping all operation until the issue is resolved.

No, the microwave enters cancel mode when E-21 is triggered, meaning it will not complete cooking cycles. You should not attempt to override or continue using the unit while this error is active. The temperature sensor is part of the microwave's thermal protection system, and operating without a functioning sensor could pose a safety risk.

Repair costs depend on the specific fault. If only a connector needs to be reseated, there may be no parts cost involved. A replacement temperature sensor typically falls in the range of $15 to $50 for the part alone. If professional labor is required, total repair costs including diagnosis and parts can range from $80 to $200 or more depending on the technician and location.

Some causes of E-21 can be addressed without professional help, such as reseating a loose connector between the sensor housing and the PCB. However, replacing the thermistor or diagnosing wiring faults requires comfort working inside a microwave, which stores high-voltage charge even when unplugged. If you are not experienced with appliance repair, a qualified technician is recommended.

Unplugging the microwave and restoring power may temporarily clear the error display, but if the underlying sensor fault is still present, E-21 will return as soon as the unit attempts to operate. A reset does not repair a failed thermistor, damaged wiring, or a loose connector. The root cause must be corrected for the error to clear permanently.