LG Heat Pump Error Code 46

Error code 46 on an LG heat pump signals an open or short circuit in the suction pipe temperature sensor. This means the control board is receiving either no signal or an out-of-range signal from the thermistor mounted on the refrigerant suction line. The unit will not operate normally until the fault is diagnosed and corrected. The first step is to check the sensor's connector at the PCB, then measure the sensor's resistance or voltage.

Continuing to operate the heat pump with error code 46 active is not recommended. The suction pipe sensor protects the compressor by monitoring refrigerant return temperature, and without a valid reading the system cannot respond properly to abnormal conditions. Running the unit with this fault could increase the risk of compressor damage over time.

A power reset may temporarily clear error code 46, but the fault will return if the underlying sensor or wiring issue has not been resolved. Because this error is triggered by an out-of-range electrical signal from the sensor, the code will reappear as soon as the system restarts and reads the same faulty condition. A proper repair of the sensor, wiring, or connection is required for the error to stay cleared.

A knowledgeable DIYer can perform the initial diagnostic steps, such as inspecting and reseating the sensor connector and visually checking the wiring harness for damage. However, measuring thermistor resistance and working near refrigerant lines requires basic electrical knowledge and appropriate tools. If the sensor has failed and needs replacement, or if the fault involves the PCB, a qualified HVAC technician should complete the repair.

If only the sensor connector needs reseating or cleaning, there may be little to no parts cost, with a service call typically ranging from $75 to $150 depending on your area. If the suction pipe thermistor itself needs replacement, parts and labor combined generally range from $100 to $300. If the PCB input circuit has failed, control board replacement can bring total costs into the $300 to $700 range or higher.