DTC P0720 Vehicle Speed Sensor.A/T (Revolution Sensor): Description
WARNING: This page is about a different car, the 2004 Nissan Quest. However, it is still accessible from the selected car via links, so may be relevant.
The revolution sensor detects the revolution of the idler gear parking pawl lock gear and emits a pulse signal. The pulse signal is sent to the TCM which converts it into vehicle speed.
Courtesy of NISSAN MOTOR CO., U.S.A.