They typically include a display or light that flashes when static electricity is discharged ... from a malfunctioning component, such as a spark plug wire that has frayed due to age or proximity ...

And it’s all because of static ... electricity, like Van de Graaff generators or Wimshurst machines can produce large electrostatic sparks. These sparks can reach around 10cm in length ...

and then discharge it with a dramatic spark. The Leyden jar is one of the first devices that allowed humans to store and release static electricity on command. It demonstrated that static charge ...