A system and method for diagnosing a home appliance are disclosed. The home appliance outputs product information as a predetermined sound signal, and transmits the sound signal to a service center of a remote site over a communication network, such that a service technician of the service center can easily check a current status of the home appliance. The diagnostic system effectively detects data using multiple synchronous signals having a time difference, quickly diagnoses a current status or fault of the home appliance, provides a service for more correctly diagnosing a faulty operation of the home appliance, and increases user satisfaction and reliability.