A liquid crystal display capable of diagnosing an abnormal driving state of a system and a liquid crystal display panel. In the liquid crystal display, a liquid crystal display panel has pixel cells arranged in a matrix pattern. A system supplies a timing synchronizing signal and video data. A timing controller generates timing control signals for driving the liquid crystal display panel in correspondence with the timing synchronizing signal inputted from the system, and re-arranges and outputs the input video data. A switching device generates a desired driving control signal. A self-diagnosing circuit applies a specific data to the liquid crystal display panel in response to the driving control signal. A driver is connected between the liquid crystal display panel and the timing controller to display the video data inputted from the timing controller on the liquid crystal display panel in correspondence with the control signals.