LG Washer Error Code E-21

E-21 on an LG washer means the control board has detected a temperature sensor open error, indicating it cannot receive a signal from the water temperature sensor. The term "open" refers to a broken electrical circuit, which can be caused by a disconnected plug, damaged wiring, or a failed sensor. The washer stops operation when this fault is detected to prevent uncontrolled temperature conditions during the wash cycle.

It is not recommended to continue running the washer with an active E-21 error. The machine cannot monitor water temperature when this fault is present, which could result in improper wash conditions or damage to certain fabrics. The washer will typically halt operation on its own when the code is triggered, so normal use is not possible until the fault is resolved.

If the fix is simply reseating a loose connector, there is no parts cost involved, only the time to diagnose and repair. Replacing a failed temperature sensor typically costs in the range of $15 to $50 for the part, with additional labor costs if a technician is hired. If the main PCB turns out to be the cause, board replacement is considerably more expensive, often ranging from $100 to $300 or more depending on the model.

Start by unplugging the washer and locating the temperature sensor and its wiring connector. Check that the connector is fully seated at both the sensor end and the PCB end, and inspect the connector pins for corrosion or damage. If the connection looks good, use a multimeter to test the sensor resistance. A sensor showing infinite resistance has failed and needs to be replaced.

A power reset by unplugging the unit for a few minutes may temporarily clear the error display, but the code will return immediately if the underlying fault is still present. Because E-21 is triggered by an ongoing open circuit condition, the sensor connection or the sensor component itself must be repaired or replaced for the error to be permanently resolved.