A method for operating a home appliance, the method comprising: starting, when an operation setting is input and an activation key is input, operation of the home appliance according to the operation setting; storing temporary data generated during said operation of the home appliance in a storage device; storing the temporary data as the diagnostic data in a memory when an initial operation time has elapsed; storing, when an error has occurred, during operation according to setting or before the initial operation time has elapsed, error data associated with the error as diagnostic data in the memory, storing the temporary data as the diagnostic data in the memory, to update the diagnostic data and initializing a post-error operation count indicating the sequence of the current operation after an error has occurred; comparing, the post-error operation count, if it has been initialized, with a reference count when said initialization has not been performed, and either: maintaining the diagnostic data as product information of the home appliance in memory when the post-error operation count is equal to or less than the reference count; or initializing the diagnostic data excluding post-error operation count data when the post-error operation count exceeds the reference count; and discarding the temporary data and maintaining the diagnostic data as product information in memory when the operation is completed according to the operation setting, if the post-error operation count has not been initialized; generating, when a command to perform fault diagnosis is input through a selector, the product information using the diagnostic data and encoding the product information to generate a digital signal including a plurality of frames, and modulating the product information for generating a frequency signal corresponding to the digital signal, and then outputting the product information as a sound signal, corresponding to the frequency signal, through a sound output device starting, when an operation setting is input and an activation key is input, operation of the home appliance according to the operation setting; storing temporary data generated during said operation of the home appliance in a storage device; storing the temporary data as the diagnostic data in a memory when an initial operation time has elapsed; storing, when an error has occurred, during operation according to setting or before the initial operation time has elapsed, error data associated with the error as diagnostic data in the memory, storing the temporary data as the diagnostic data in the memory, to update the diagnostic data and initializing a post-error operation count indicating the sequence of the current operation after an error has occurred; comparing, the post-error operation count, if it has been initialized, with a reference count when said initialization has not been performed, and either: maintaining the diagnostic data as product information of the home appliance in memory when the post-error operation count is equal to or less than the reference count; or initializing the diagnostic data excluding post-error operation count data when the post-error operation count exceeds the reference count; and maintaining the diagnostic data as product information of the home appliance in memory when the post-error operation count is equal to or less than the reference count; or initializing the diagnostic data excluding post-error operation count data when the post-error operation count exceeds the reference count; and discarding the temporary data and maintaining the diagnostic data as product information in memory when the operation is completed according to the operation setting, if the post-error operation count has not been initialized; generating, when a command to perform fault diagnosis is input through a selector, the product information using the diagnostic data and encoding the product information to generate a digital signal including a plurality of frames, and modulating the product information for generating a frequency signal corresponding to the digital signal, and then outputting the product information as a sound signal, corresponding to the frequency signal, through a sound output device