LG Air Conditioner Error Code 57

Error code 57 on an LG air conditioner indicates a communication error between the main PCB and the inverter PCB. Specifically, the inverter PCB is not receiving the signal from the main PCB. The system shuts down when this happens to protect the compressor from uncontrolled operation. Diagnosis starts with checking the communication wire connections between the two boards.

No, the unit will typically shut down automatically when error code 57 is triggered, which is a protective measure. Attempting to force the system to run without resolving the underlying communication fault could result in uncontrolled compressor operation and potential component damage. The system should remain off until the fault is diagnosed and corrected.

Repair costs vary depending on the root cause. If the fix is simply reseating a loose connector, the cost is primarily the diagnostic labor fee, which typically ranges from $75 to $150. If a wiring harness needs replacement, parts and labor combined may run $100 to $300. Replacing either the main PCB or inverter PCB can cost significantly more, often in the range of $300 to $700 or higher depending on the specific model and part pricing.

A knowledgeable DIYer can start by checking whether the communication wire connectors between the main PCB and inverter PCB are fully seated and free of visible damage or corrosion. If the connectors appear secure and undamaged, further diagnosis requires testing signal integrity and inspecting the boards themselves, which is generally better handled by a qualified technician. Replacing control boards also involves working with high-voltage components and should be approached with caution.

A power reset may temporarily clear the error, but if the underlying cause such as a loose connector, damaged wire, or faulty board is still present, the code will return. Resetting without addressing the root cause is not a reliable fix and can delay proper diagnosis. If the error returns after a reset, a thorough inspection of the communication wiring and both PCBs is necessary.