Genuine OEM Volkswagen Coolant Temperature Sensor, part number 251919501D. This vital sensor is responsible for accurately measuring the temperature of the engine's coolant, providing essential data to the engine control unit. This information is crucial for precise fuel injection, ignition timing, and fan operation, ensuring optimal engine performance, fuel efficiency, and emissions control. Choosing a genuine OEM sensor guarantees exact calibration and signal characteristics, which are critical for accurate readings and preventing engine management issues.