DTC P0500: Vehicle 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 signal not received by PCM after the following conditions are met: transaxle range switch is placed in "D", "S" or "L" position, engine coolant temperature is 140°F (60°C) or more and turbine speed is 1500 RPM or more.