DTC P1784-00: Hi Cut Valve Stuck Off/R-3-5 Cut Valve Stuck On (TCM) (Us): Outline

WARNING: This page is about a different car, the 2020 Mazda CX-30. However, it is still accessible from the selected car via links, so may be relevant.

DTC P1784:00 (TCM, EV6A-EL, EV6AX-EL, US) DETECTION CONDITION AND POSSIBLE CAUSE

System malfunction location	Hi cut valve stuck off/R-3-5 cut valve stuck on
Detection condition	Under the following conditions, hi cut valve stuck-off or R-3-5 cut valve stuck-on detected by combination of gear ratio malfunction and oil pressure switch pattern malfunction: Engine is running. ATF temperature is 20°C {68°F} or more. There is no correlation between vehicle speed signal from DSC HU/CM and output shaft speed sensor signal. Turbine/input shaft speed sensor and output shaft speed sensor DTC is not recorded.
Fail-safe	Inhibits malfunctioning gear. Limits engine torque. Inhibits learning control. Inhibits neutral idle control.
Possible cause	ATF is less than specified value Hi cut valve malfunction R-3-5 cut valve malfunction Clutch burnt
System wiring diagram	Not applicable
Connector diagram	Not applicable