In a computing device, a computerized method and a non-transitory storage medium are applied in checking a stored wiring diagram for high-noise components in close proximity to signal lines. An electronic component is selected in a PCB wiring file. A checking range of the selected electronic component is determined for searching for one or more signal transmission lines which pass within the checking range in the PCB wiring file. Basic information of the one or more signal transmission lines is recorded into a result list which is displayed on a display unit of the computing device.