There are many sensors included as a part of the trans components- manual in your Nissan D21. The primary task of a sensor is to measure an element of the engine function and generate a warning signal if something is malfunctioning. These pieces could evaluate shaft speed, fluid temperature, or transmission speed.
The job of the transmission is to transfer the power of the engine throughout the drive train to the front and rear tires of the Nissan D21. When operating correctly, the transmission moves between gears and maintains driving stability. Without the assistance of sensors, complete failure could occur. StockWiseAuto.com has the parts you need when sensors go bad.