DTC P0731: Incorrect 1ST Gear Ratio: 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 turbine speed and vehicle speed under preset value, with ignition switch in ON position. ATF temperature must be greater than 68°F (20°C), transaxle in first gear ("D" position), engine speed 500 RPM or more, turbine speed 75 RPM or more, vehicle speed 4-37 MPH, throttle opening angle at 6.25 percent or more, brake pedal released, and DTC P0500, P0710, P0715, P0750, P0755 or P0760 are not output.