LG Heat Pump Error Code E221

E221 indicates an OPEN or SHORT error in the outdoor ambient temperature sensor circuit. The outdoor PCB has detected a resistance reading from the NTC thermistor that falls outside the acceptable range, meaning the sensor is either disconnected, failed, or has a wiring fault. The system cannot accurately read outdoor temperature, so it shuts down to prevent unsafe or inefficient operation.

No, it is not advisable to continue running the unit while E221 is active. The outdoor temperature sensor data is used to control defrost cycles and compressor operation, and running without accurate ambient temperature readings can cause the system to operate outside safe parameters. Address the fault before resuming normal operation.

Repair costs vary depending on the root cause. If only the outdoor temperature sensor thermistor needs replacement, parts typically range from $15 to $60, and a service call with labor can bring the total to $100 to $250. If the outdoor PCB is at fault, parts and labor costs can range from $300 to $600 or more depending on the unit model and technician rates.

Some causes are approachable for a knowledgeable DIYer. Start by checking whether the sensor connector is fully seated on the outdoor PCB and inspect the wiring harness for obvious damage. If the connector is secure, use a multimeter to measure the sensor resistance and compare it against the temperature-resistance reference table. If the sensor reads out of range, replacing the thermistor is a relatively straightforward repair, though working on the outdoor unit should be done with the system powered off.

A power reset may temporarily clear the error display, but the fault will return if the underlying sensor or wiring problem has not been resolved. Resetting without repairing the cause is not a fix. Diagnose and correct the sensor circuit issue first, then confirm the error does not reappear after restoring power.