A spark plug is a device that produces an electrical spark, which ignites the mixture of fuel and air in the engine's combustion chambers. A spark plug initiates the combustion in the internal combustion engine.
A spark plug operates by directing electrical current to flow through a center electrode, forming a spark across an electrode gap. This completes the circuit to a ground electrode.
Spark plugs are also used to measure ionization in the cylinders. This ionic current measurement is used to replace the ordinary cam phase sensor, knock sensor and misfire measurement function. Spark plugs are also utilized in other applications, such as furnaces where a combustible fuel or air mixture must be ignited.