Genuine OEM Volkswagen Knock Deflector with Wiring, part number 078905377. This sensor detects engine knock, which is the uncontrolled combustion of fuel in an engine cylinder. It is a critical component for engine performance and longevity, helping to prevent engine damage by allowing the engine control unit to adjust ignition timing. The part is located in the engine assembly. Genuine OEM sensors ensure precise calibration and signal characteristics for reliable engine operation.