LG Heat Pump Error Code E354

E354 indicates a low pressure sensor breakaway fault. This means the control board has lost the signal from the low-side refrigerant pressure sensor, either because the sensor failed, a wiring connection was lost, or the refrigerant pressure dropped too low to register. The system will typically shut down to prevent compressor damage until the fault is cleared.

It is not recommended to continue running the heat pump while E354 is active. Without a valid low pressure reading, the control system cannot properly protect the compressor from running under a loss-of-charge or other low-pressure condition. Continued operation could result in compressor damage, which is significantly more expensive to repair.

Repair costs vary depending on the cause. Replacing a low pressure sensor typically costs between $80 and $200 for parts and labor. If the fault is due to a refrigerant leak, costs can range from $200 to $600 or more depending on the extent of the leak repair and the amount of refrigerant needed. Control board replacement, if required, is generally the most expensive option, ranging from $300 to $700 or higher.

Some causes of E354, such as a loose sensor connector or a damaged wire, can be addressed by a knowledgeable DIYer comfortable working with electrical components. However, if the fault involves a refrigerant leak or recharge, federal regulations require a certified HVAC technician with an EPA Section 608 certification to handle refrigerants. Sensor replacement is also possible for DIYers, but correct diagnosis should be confirmed before purchasing parts.

A power reset may temporarily clear the error display, but if the underlying cause, such as a failed sensor, broken wire, or low refrigerant charge, has not been corrected, the E354 fault will return once the system restarts and attempts to read the sensor. A reset should only be used as part of the diagnostic process, not as a long-term fix.