LG Air Conditioner Error Code E505

E505 indicates that the LG air conditioner's self-diagnostic routine has detected a fault with the high pressure sensor. The control board checks the voltage signal from this sensor and triggers E505 when that signal falls outside the expected range. The unit shuts down as a precaution to prevent operating with unreliable pressure data. A technician should begin diagnosis by inspecting the sensor connector and measuring voltage between pins 3 and 4.

No, you should not attempt to bypass or ignore the E505 shutdown. The high pressure sensor is a safety component that helps prevent compressor damage and refrigerant circuit failures caused by overpressure. Operating the unit without a functioning sensor means the system has no protection against dangerous pressure buildup. Leave the unit off until the fault is diagnosed and resolved.

A power reset may temporarily clear the E505 code, but if the underlying fault with the high pressure sensor or its wiring has not been corrected, the error will return once the self-diagnostic routine runs again. Resetting the unit without fixing the problem does not make it safe to operate. Use a reset only as part of a diagnostic process after a repair has been made to verify the fault is resolved.

Some causes of E505, such as a loose or corroded connector at the high pressure sensor, can be inspected and corrected by a knowledgeable DIYer. However, diagnosing sensor voltage output, checking refrigerant system pressures, or replacing the sensor or control board requires tools and knowledge that most homeowners do not have. If the wiring and connector look intact, it is best to call a qualified HVAC technician to continue diagnosis safely.

Repair costs vary depending on the root cause. Connector cleaning or reseating may only require a service call fee, typically in the range of $75 to $150. Replacing the high pressure sensor itself generally adds $50 to $200 in parts depending on the specific model. If the control board is at fault, board replacement can range from $200 to $600 or more including labor. A refrigerant-related cause may add refrigerant handling fees on top of those estimates.