LG Heat Pump Error Code E278

E278 indicates a low pressure sensor breakaway fault. This means the heat pump's control board has lost the signal from the low-side refrigerant pressure sensor, either because the sensor has physically disconnected, the wiring has failed, or the sensor itself has malfunctioned. The system shuts down to prevent compressor damage from running without reliable pressure monitoring.

A reset may temporarily clear the E278 code if the fault was caused by a momentary connection interruption, but the error will return if the underlying problem is not resolved. A persistent E278 after reset indicates the sensor, connector, or wiring needs physical inspection and likely repair or replacement.

Repair costs depend on the root cause. A simple connector reseating may fall within a standard diagnostic service call fee, typically in the range of $75 to $150. Sensor replacement parts and labor could range from $150 to $400. If a refrigerant leak is involved, costs can rise to $400 to $900 or more depending on leak location and the amount of refrigerant needed.

Some causes, such as a loose electrical connector at the sensor, can be addressed by a knowledgeable DIYer after powering down the unit. However, if the fault involves a refrigerant leak, sensor replacement on a pressurized fitting, or main board wiring repair, a certified HVAC technician is required. Refrigerant handling is legally restricted to certified professionals in most jurisdictions.

No. The heat pump should not be forced to run while displaying E278. The low pressure sensor protects the compressor from damage caused by low refrigerant charge or restricted flow conditions. Operating without reliable pressure monitoring risks compressor failure, which is a much more costly repair than addressing the sensor fault.