LG Air Conditioner Error Code 122

Error code 122 means the discharge temperature sensor for constant speed compressor 2 on the sub1 outdoor unit is reading an open or short circuit. This sensor monitors the temperature of refrigerant exiting the compressor on the discharge pipe. The control board cannot get a valid temperature reading, so it flags the fault to protect the compressor from running unmonitored. The issue is typically in the sensor itself, its lead wire, or the connector.

Operating the system with this fault active is not recommended. The discharge temperature sensor on the compressor is a protective component, and without a valid reading, the control system cannot detect if the compressor is overheating. Continued operation without this protection could result in compressor damage, which is a far more costly repair than addressing the sensor fault.

A power reset may temporarily clear the fault code, but the error will return quickly if the underlying problem with the sensor, wiring, or connector has not been corrected. Because this fault is based on a measurable electrical condition that the control board reads continuously, the code will reappear as soon as the system restarts and detects the same open or short circuit. A proper repair of the sensor circuit is required for the code to stay cleared.

A knowledgeable DIYer can perform the initial diagnostics, including inspecting the sensor connector and lead wire for visible damage, loose connections, or corrosion. If the sensor needs to be replaced, that work is straightforward if you are comfortable working on outdoor units. However, if the fault points to the control board or involves refrigerant system access, a licensed technician should handle the repair.

If the fix is simply reseating a loose connector or cleaning corroded terminals, the cost is minimal, primarily a service call fee ranging from roughly 75 to 150 dollars. Replacing the discharge temperature sensor itself is generally an inexpensive part, with total repair costs typically ranging from 100 to 250 dollars. If the outdoor unit control board is the root cause, parts and labor costs can range from 300 to 600 dollars or more depending on the unit model.