DTC P0715: Input/Turbine Speed Sensor Circuit Fault: Description
WARNING: This page is about a different car, the 2002 Mazda Millenia and 2001 Mazda Millenia. However, it is still accessible from the selected car via links, so may be relevant.
DTC will set if vehicle speed is 25 MPH and input/turbine speed sensor signal is not input to PCM for one second or more.