Genuine OEM Audi Exhaust Temperature Sensor, part number 05L919529D. This sensor monitors the temperature of the exhaust gases, providing critical data to the engine control unit (ECU) for optimizing fuel injection, ignition timing, and emissions control systems. It is marked as number 1 in the diagram. The sensor is designed for precise temperature measurement under harsh exhaust conditions. Genuine OEM sensors are vital for maintaining exact calibration and signal characteristics, ensuring accurate engine management and compliance with emissions regulations.