LG Heat Pump Error Code E331

E331 indicates a high pressure sensor OPEN or SHORT error. The control board checks the sensor signal voltage before allowing the compressor to start, and has detected a voltage either below 0.4V (SHORT) or above 4.2V (OPEN). The unit will not allow the compressor to run until the fault is resolved.

The unit will not allow the compressor to operate while E331 is active, so the system is protecting itself from running without a valid pressure sensor signal. You should not attempt to bypass this protection, as the high pressure sensor is a critical safety component. Have the fault diagnosed and repaired before returning the unit to normal operation.

Repair costs depend on the specific cause. If the fix is a connector cleaning or a wiring repair, the labor cost is typically modest, ranging from roughly $75 to $200 depending on technician rates and access. If the high pressure sensor itself needs replacement, parts and labor combined generally fall in the range of $150 to $400. A control board replacement, if required, would be the most expensive outcome and could range from $300 to $700 or more.

Start by inspecting the high pressure sensor wiring and connector for corrosion, damage, or loose connections, as these are the most frequent causes. If the wiring checks out, test the sensor output voltage with a multimeter to determine whether it falls within the 0.4V to 4.2V operating range. A sensor that reads outside that range under normal conditions will need to be replaced. If both the wiring and sensor test correctly, the control board input circuit may be at fault.

A power reset may temporarily clear the error code, but E331 is detected each time the system prepares to start the compressor. If the underlying wiring or sensor fault is still present, the code will return as soon as the unit attempts to start. A reset alone is not a repair, and the sensor circuit needs to be physically inspected and corrected.