This coil-on-plug and signal probe can easily catch an automobile engine's ignition waveform. The ignition waveform is a window, through which we can see what happened in the engine combustion chambers. It determines whether the ignition plug needs to be replaced or cleaned. Does the fuel injector in the electronic fuel injection system work well? Is there any problem with the leakproofness of the air cylinder? Does the gap between ignition plugs get larger? Does the electrode shape of the ignition plug become sharp? Is there too much oil pollution or carbon deposition on the ignition plugs? Does the insulating property of the ignition plug get worse? Is there any problem with the power supply system of the storage battery?