The knock sensor prevents damaging spontaneous ignition. The knocking effect is created by acyclic uncontrolled combustion, which produces extreme local temperatures in the cylinder. These high heat quantities place a severe strain on engine components such as the pistons, valves and cylinder head, and can lead to damage. The knock sensor registers the body-borne sound of the engine and converts it into electrical pulses. The engine control unit cross-checks the measured pulses against the stored specification values and intervenes to control the engine, fuel injection and ignition as necessary, before the combustion reaches the knock limit. The knock sensor performs an additional function in detecting the fuel quality. The higher the octane number (RON), the more knock-proof is the fuel. This means 98 RON Super Plus grade fuel ignites at a higher temperature than normal 95 RON petrol. If only a lower quality of fuel is available on occasion, the engine control unit automatically corrects the ignition timing based on the information from the knock sensor. This prevents damage to the engine.