DTC P0721-00: Secondary Pulley Speed Sensor Circuit Range/Performance: General Description
WARNING: This page is about a different car, the 2021 Kia Soul. However, it is still accessible from the selected car via links, so may be relevant.
The turbine speed sensor is a vital unit that measures the internal turbine speed (IVT - Intelligent Variable Transmission).
The drive pulley speed sensor is to detect the speed of drive pulley.
The output speed sensor is to detect number of rotation of IVT output shaft and transfers to PCM.