LG HVAC Error Code 46

Error code 46 means the outdoor unit control board (PCB) has detected that the suction line thermistor is reading as open-circuit or shorted. The suction line thermistor monitors refrigerant temperature on the low-pressure side of the system as it returns to the compressor. The system uses this sensor reading for operational control, and an invalid signal causes the unit to fault out. The code points to a sensor, wiring, connector, or PCB issue on the outdoor unit.

The system will typically not operate normally while error code 46 is active, as the PCB cannot properly monitor suction line temperature. Attempting to force operation without a valid suction line temperature reading could allow the compressor to run under unmonitored refrigerant conditions. It is best to leave the unit off until the fault is diagnosed and resolved.

A power reset may temporarily clear the fault and allow the unit to restart, but if the thermistor, wiring, or PCB has an actual defect, the code will return quickly. Resetting without addressing the root cause does not fix the underlying problem and can delay proper diagnosis. The correct approach is to test the thermistor resistance, inspect the wiring, and address whichever component is outside of specification.

A knowledgeable DIYer can inspect the wiring harness and reseat the connector at the thermistor and PCB, which costs nothing and occasionally resolves the fault. Testing the thermistor resistance requires a digital multimeter and knowledge of how to test the sensor submerged in water at a measured temperature, comparing results against 2,800 ohms at 38 degrees Celsius or 10,000 ohms at 10 degrees Celsius. Replacing the thermistor is a straightforward part swap. However, if the PCB needs replacement, most homeowners prefer to have a certified technician handle that step.

If only the suction line thermistor needs replacement, parts and labor typically fall in the range of $75 to $200 depending on the specific model and local labor rates. If the outdoor unit PCB is at fault, the repair cost increases significantly, often ranging from $300 to $700 or more depending on board pricing and labor. Getting a diagnostic visit from a certified technician first will clarify which component is responsible before committing to parts costs.