LG Heat Pump Error Code E266

E266 on an LG heat pump indicates a Sump Sub 1 breakaway error, meaning the Sump Sub 1 temperature sensor has physically separated from its mounting location in the unit. The system shuts down or restricts operation because it cannot receive valid thermal data from that sensor. The error is specifically tied to physical displacement of the sensor rather than a wiring fault or sensor burnout.

It is not recommended to continue operating the heat pump while the E266 error is active. The system relies on the Sump Sub 1 sensor to monitor sump temperature and protect components from running outside safe conditions. Operating without a valid sensor reading could allow thermal conditions to go undetected, potentially causing damage to the unit over time.

If the repair only requires reseating the dislodged sensor, the cost is primarily a service call fee, which typically ranges from around $75 to $150 depending on your location and technician. If the sensor clip or bracket needs replacement, parts costs are generally modest, in the range of $10 to $40. A full sensor replacement, if the component is found to be defective, may bring total repair costs to somewhere between $100 and $250 including labor.

Start by powering down the unit and visually inspecting the Sump Sub 1 temperature sensor inside the heat pump. If the sensor has pulled free from its bracket or clip, reseat it firmly in its correct mounting position and ensure it is secured. After reassembly, restore power and check whether the error clears. If the fault persists after reseating, inspect the sensor connector and wiring for damage, and consider testing or replacing the sensor itself.

A power reset alone is unlikely to permanently clear the E266 error if the underlying cause has not been addressed. Because the fault is triggered by a physically displaced sensor, the error will typically return as soon as the control board checks for the sensor signal again. The sensor must be properly reseated and secured before a reset will result in normal operation.