LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Mazda >> 2021 >> 3 Select, 4D Hatchback, AWD >> Repair and Diagnosis (Single Page) >> Engine Performance >> System >> On-Board Diagnostic - Engine Control System (VINS 7, L, M) (4 Of 4) >> DTC U2121-00: Can Communication: Communication Error To Vehicle Control Module (VCM) >> Outline
April 5, 2026: LEMON Manuals is launched! Read the announcement.

DTC U2121-00: Can Communication: Communication Error To Vehicle Control Module (VCM): Outline

DTC U2121:00 (PCM, VINs 7, L, M, US) DETECTION CONDITION AND POSSIBLE CAUSE

System malfunction location CAN communication: communication error to vehicle control module (VCM)
Detection condition
  • Communication error between the PCM and vehicle control module (VCM) continues for 5 s or more.
Fail-safe
  • Not applicable
Possible cause
  • CAN communication line malfunction between PCM and vehicle control module (VCM)
  • Vehicle control module (VCM) malfunction (built-into body control module (BCM)
  • PCM malfunction
System wiring diagram
  • Not applicable
Connector diagram
  • Not applicable