coil-on plug and signal probe can catch the ignition waveform of automobile engine easily. 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 clean. Does the fuel injector in the electronic fuel injection system work well? Is there any problem in the 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 ignition plug get worse? Is there any problem in the power supply system of storage battery?