DTC U0121-00: Communication Error With DSC HU/Cm [Vehicle Control Module (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 U0121:00 (VEHICLE CONTROL MODULE - US) DETECTION CONDITION AND POSSIBLE CAUSE

System malfunction location	Communication error with DSC HU/CM
Detection condition	The vehicle control module (VCM) cannot receive CAN signal from DSC HU/CM for 10 s.
Fail-safe	(See DTC TABLE [VEHICLE CONTROL MODULE (US)] .)
Possible cause	Malfunction in CAN communication line between vehicle control module (VCM) and DSC HU/CM DSC HU/CM malfunction Vehicle control module (VCM) malfunction (built into body control module (BCM))
System wiring diagram	Not applicable