DTC P0740: Torque Converter Clutch System 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 difference between turbine speed and engine speed greater than preset value. ATF temperature must be greater than 68°F (20°C), transaxle in fourth gear ("D" position), engine speed 500 RPM or more, turbine speed 75 RPM or more, throttle opening angle other than closed throttle position, vehicle speed at 47-64 MPH, brake pedal released, TCC activated, O/D OFF switch off, and DTC P0500, P0710, P0715, P0750, P0755 or P0760 are not output.