DTC P0734: Incorrect 4TH Gear Ratio: Description
WARNING: This page is about a different car, the 2002 Mazda 626 and 2001 Mazda 626. 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. ATF temperature must be above 68°F (20°C), transaxle in fourth gear ("D" position), engine speed 500 RPM or more, turbine speed 75-4986 RPM, vehicle speed 47-64 MPH, brake pedal released and DTC P0500, P0710, P0715, P0750, P0755 or P0760 are not output.