This sensor is situated on top of the transmission where the Secondary pulley is fitted.
and sometimes on the back of the transmission for the Primary pulley Most transmissions have more than 1 sensor.
It is measuring the revolutons of the pulleys and other running components and send this information to the TCU (Transmission control unit ) Be careful with diagnoses because this sensor is there for checking if the
mechanical parts are working OK. This means the sensor can be OK but there is an mechanical fault internal.