DTC U2121-87: Communication Error With Vehicle Control Module (VCM) [Adaptive Front Lighting System (AFS) Control Module]

WARNING: This page is about a different car, the 2024 Mazda CX-30. However, it is still accessible from the selected car via links, so may be relevant.

U2121: 87 (ALH/AFS/ALV) DETECTION CONDITION AND POSSIBLE CAUSE

System malfunction location	Communication error with vehicle control module (VCM)
Detection condition	The adaptive LED headlights control module cannot receive CAN signal from the vehicle control module (VCM).
Fail-safe	Control of the headlight auto leveling system is continued. Perform the following controls with the adaptive LED headlights turned on. Turn off glare-free high beam. Set wide-range low beam as basic light distribution.
Possible cause	Malfunction in CAN communication line between vehicle control module (VCM) and adaptive LED headlights control module NOTE: Perform the malfunction diagnosis according to the troubleshooting procedure for the multiplex communication system. (See MALFUNCTION DIAGNOSIS FLOW [CONTROLLER AREA NETWORK (CAN)] .)
Repeatability verification procedure	Not applicable
System wiring diagram	Not applicable