LG Heat Pump Error Code 43

Error code 43 on an LG heat pump signals that the high pressure sensor circuit has been detected as open or short circuited. The control board monitors the sensor's output signal continuously, and when the reading falls outside acceptable parameters, the unit stops operation and displays this code. The fault can originate at the sensor connector, the wiring harness, the sensor itself, or the PCB.

No, you should not attempt to bypass or continuously reset the unit while this fault is active. The high pressure sensor is a safety-critical component that protects the compressor and refrigerant circuit from dangerous overpressure conditions. Operating the system without a functioning pressure sensor could result in compressor damage or refrigerant system failure.

A power reset may temporarily clear the code and allow the unit to restart, but the fault will return if the underlying wiring or sensor issue has not been resolved. Repeatedly resetting without addressing the root cause risks running the system without proper high pressure protection. A full diagnostic of the sensor circuit should be completed before returning the unit to normal operation.

A knowledgeable DIYer can safely start by checking the sensor connector for looseness or corrosion and reseating it. If that does not clear the fault, measuring the sensor resistance or voltage with a multimeter is the next step. However, replacing the sensor or working on the refrigerant circuit requires EPA certification, so those steps should be left to a licensed technician.

If the fix is simply reseating a loose connector, there is no parts cost involved. Replacing the high pressure sensor typically costs between 50 and 150 dollars for the part, plus labor. If the PCB requires replacement, total repair costs can range from 300 to 700 dollars or more depending on the model and service rates in your area.