ERROR CODE SEARCH. By checking the error code, you are able to identify the status and the issue of the air conditioner/air conditioning system. The Error Code Search offers information on the cause of the malfunction and the status of your air conditioner by entering the error code. system code meaning; 00: normal: ua: indoor-outdoor unit combination fault: u0: refrigerant shortage: u2: drop voltage or main circuit overvoltage: u4: failure of transmission (between indoor unit and outdoor unit) zFEQ.