LG Heat Pump Error Code E171

E171 indicates that during the piping check procedure, the LG heat pump detected no change in the evaporator outlet temperature. This tells the control system that refrigerant is either not circulating through the evaporator coil or that the sensor monitoring that point is not reading correctly. The piping check is a built-in diagnostic routine designed to confirm proper refrigerant flow before or during operation.

Running the system with E171 active is not recommended. The error indicates the heat pump cannot confirm proper refrigerant circulation, and operating under those conditions could cause compressor damage due to inadequate lubrication or cooling. The unit may shut down automatically to protect itself, but powering it down manually until the fault is resolved is the safest approach.

A power reset may temporarily clear the E171 code and allow the unit to restart, but the error will return if the underlying problem is not corrected. Because E171 is triggered during a specific piping check routine, the fault condition that caused it, whether a sensor issue, refrigerant problem, or valve fault, must be identified and repaired before the system will operate reliably without the code returning.

Some causes of E171, such as a closed service valve or a loose sensor connector, can be addressed without specialized equipment. However, diagnosing a refrigerant charge issue requires manifold gauges and EPA certification to handle refrigerant legally, and replacing an expansion valve or thermistor requires technical knowledge of the system. Most homeowners will need a qualified HVAC technician to properly diagnose and repair this fault.

Repair costs vary depending on the root cause. A sensor replacement typically ranges from around $75 to $200 including parts and labor. Refrigerant recharge or leak repair can range from $150 to $600 or more depending on the type of refrigerant and amount needed. Expansion valve replacement tends to fall in the $200 to $500 range. A diagnostic service call alone typically costs $75 to $150.