LG Air Conditioner Error Code 157

Error code 157 means the high pressure sensor on the sub3 outdoor unit has been detected as open or short circuited. This sensor monitors refrigerant pressure on the high side of the system and sends a signal to the PCB. When that signal falls outside expected parameters, the system logs this code and may disable compressor operation to avoid damage.

Running the system while this error is active is not recommended. The high pressure sensor is a critical safety component, and operating without reliable pressure feedback can allow the system to reach damaging or unsafe refrigerant pressures. The system may already be limiting or preventing compressor operation as a protective measure.

A power reset may temporarily clear the code, but if the underlying fault in the sensor, wiring, or connector is still present, the error will return once the system resumes normal operation. A reset should only be used as part of a diagnostic process, not as a long-term fix. The root cause must be identified and corrected to permanently resolve the error.

A knowledgeable DIYer can safely check whether the sensor connector is fully seated on the PCB, which is the first recommended diagnostic step. However, testing sensor resistance, tracing wiring faults, and replacing refrigerant-side components typically requires proper tools and training. If the connector check does not resolve the error, a qualified HVAC technician should be brought in.

Repair costs vary depending on the root cause. A simple connector reseating during a service call might cost between $75 and $150 for labor alone. Sensor replacement typically adds $50 to $150 in parts. PCB replacement is the most expensive outcome, with parts and labor potentially ranging from $300 to $700 or more depending on the unit and region.