LG Heat Pump Error Code E424

E424 indicates a high pressure sensor OPEN or SHORT fault. The control board monitors the sensor's voltage signal and flags this error when the voltage drops below 0.4V (SHORT) or rises above 4.2V (OPEN). The fault is detected when the compressor is about to start, and the unit will not run until the sensor circuit is restored to a valid signal range.

A power reset may temporarily clear the E424 code, but if the underlying wiring or sensor fault is still present, the error will return as soon as the compressor attempts to start again. A reset alone is not a fix and should be used only as part of diagnosing whether the fault is intermittent or persistent.

Repair costs vary depending on the root cause. If the fix is simply reseating a connector or repairing a damaged wire, labor costs alone may run in the range of $75 to $200. If the high pressure sensor requires replacement, parts and labor combined could range from $150 to $400 or more depending on the model and local labor rates. A control board replacement, if needed, would be at the higher end of the cost spectrum.

Some causes of E424, such as a loose connector or visibly damaged wire, can be addressed by a knowledgeable DIYer comfortable working with low-voltage wiring. However, accessing the sensor and its wiring typically requires disassembling part of the unit, and any work near the refrigerant circuit should be left to a certified technician. If the sensor itself needs replacement, a professional should handle the repair.

The system will typically prevent the compressor from operating when E424 is active, so the risk of immediate damage is low. However, you should not attempt to bypass the error or force operation, as the high pressure sensor is a safety component designed to protect the compressor from dangerous pressure conditions. Have the fault diagnosed and repaired promptly.