LG Heat Pump Error Code E165

E165 means the system detected no change in the evaporator outlet temperature during the piping check sequence. This automated test verifies that refrigerant is flowing through each indoor unit. When the EVAP OUT sensor shows no temperature shift, the system flags E165 and stops the test. The most common causes are an indoor unit address mismatch or an Electronic Expansion Valve that is not operating.

E165 occurs during the piping check commissioning sequence, not during normal operation. The system halts the check when this code appears, so normal heating or cooling may be unavailable until the issue is resolved. You should not attempt to bypass the piping check, as it is designed to confirm proper refrigerant circulation before full operation begins.

A power reset may clear the code temporarily, but the error will return when the system runs the piping check again if the underlying cause has not been resolved. The piping check must complete successfully for the system to enter normal operation mode. Resetting without fixing the address mismatch or EEV issue will not result in a lasting repair.

Checking and correcting the indoor unit address setting is something an experienced DIYer can attempt using the installation documentation for the specific unit. Inspecting the EEV wiring harness for a loose connection is also a low-risk check. However, measuring EEV coil resistance, diagnosing refrigerant flow issues, and replacing components like the EEV or sensors generally require a certified HVAC technician and proper tools.

If the fix is simply correcting an address configuration, there may be no parts cost and only a service call fee, typically in the range of $75 to $150. If the EEV coil needs replacement, parts and labor can range from $150 to $400 depending on the unit and local labor rates. A full EEV valve body replacement or sensor replacement may push costs higher, often $300 to $600 or more.