DTC U0402-00: Abnormal Message From Transmission/Transaxle: Notes

WARNING: This page is about a different car, the 2016 Mazda CX-5. However, it is still accessible from the selected car via links, so may be relevant.

DTC	U0402:00		Abnormal message from transmission/transaxle
DETECTION CONDITION		The DSC HU/Control Module received error signals from the transmission/transaxle for 1 s or more with the ignition switched ON (engine off or on).
FAIL-SAFE FUNCTION		Refer to "DTC TABLE " and "Fail-safe Function Malfunction Contents". (See ON-BOARD DIAGNOSIS [DYNAMIC STABILITY CONTROL (DSC)] .)
POSSIBLE CAUSE		The transmission/transaxle could not send a normal signal temporarily. (DTCs are stored in the TCM.) Transmission/transaxle malfunction TCM malfunction
SYSTEM WIRING DIAGRAM		-