The Bosch Knock Sensor - 0261231113 is a device that detects and measures engine knock or detonation in a vehicle's engine. It is designed to monitor the vibrations and sounds produced by the engine and send this information to the engine control unit (ECU). The ECU then adjusts the engine's timing and fuel injection to prevent damage and improve performance. This knock sensor is compatible with a variety of vehicle makes and models and is a crucial component in ensuring the smooth and efficient operation of a vehicle's engine.