LG Heat Pump Error Code E342

E342 indicates a SUMP TEMP FIXED 1 sensor error on an LG heat pump. The control board has detected that the sensor signal voltage is either above 4.95V (open circuit, reading below -30°C) or below 0.5V (short circuit, reading above 151°C). This fault is only triggered when the outdoor temperature is above -10°C, and it prevents the system from operating without reliable sump temperature data.

You should not continue running the heat pump while E342 is active. The sump temperature sensor provides critical data for protecting the compressor and managing refrigerant conditions. Operating without a valid sensor reading risks compressor damage, which is a much more costly repair than fixing the sensor itself.

A power reset may temporarily clear the error code from the display, but if the underlying sensor fault is still present, the E342 code will return once the unit restarts and the control board re-checks the sensor signal. A reset is useful for confirming whether the fault is intermittent, but it is not a fix. The connector and sensor resistance should be tested before concluding the problem is resolved.

Some steps are DIY-friendly, such as inspecting the sensor connector for a loose connection and reseating it firmly. Measuring resistance across the sensor terminals with a multimeter is also manageable for someone comfortable with basic electrical testing. However, if the thermistor or wiring harness needs replacement, working on the outdoor unit refrigerant system and control board wiring is typically best handled by a qualified technician.

If the fix is simply reseating a loose connector, there may be no parts cost, only a service call fee typically in the range of $75 to $150. If the thermistor sensor itself needs replacement, parts and labor combined generally run between $150 and $350 depending on your location and the technician's rates. A damaged wiring harness can push costs higher depending on the extent of the damage.