LG Heat Pump Error Code E351

E351 indicates a high pressure sensor OPEN or SHORT error on an LG heat pump. The system detected that the high pressure sensor signal voltage was either below 0.4V (SHORT) or above 4.2V (OPEN) at the point when the compressor was preparing to operate. This causes the system to shut down as a protective measure. The fault typically points to a wiring or sensor problem rather than an actual refrigerant pressure issue.

No, you should not attempt to bypass or ignore the E351 error. The high pressure sensor is a critical safety component that prevents the compressor from operating under unsafe pressure conditions. The system is intentionally preventing the compressor from starting until the fault is resolved, and forcing operation could result in compressor damage or a refrigerant system failure.

Repair costs vary depending on what is found during diagnosis. If only a wiring repair or connector cleaning is needed, labor costs may range from $75 to $200 depending on your area. Replacing the high pressure sensor typically adds $50 to $150 in parts cost on top of labor. If the control board turns out to be the cause, costs can rise significantly, potentially ranging from $300 to $600 or more for parts and labor.

Start by checking all wiring connected to the high pressure sensor for damage, loose connections, or corrosion at the connector pins. If the wiring appears intact, use a multimeter to verify continuity throughout the harness and confirm that the sensor is producing a voltage within its valid operating range. If the sensor is producing an out-of-range signal with good wiring, the sensor will need to be replaced. A qualified technician should handle refrigerant-side component work.

A power reset may temporarily clear the displayed fault code, but the E351 error will return as soon as the system attempts to start the compressor again if the underlying wiring or sensor problem has not been corrected. The fault is detected during the compressor ready-to-operate phase, so it will reappear in the next startup cycle until the root cause is repaired.