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DTC U0121:00 [PCM (SKYACTIV-G (E))]

id0102t43277u1

Outline

System malfunction location

Vehicles with Mazda M Hybrid:

•  CAN communication: communication error to electronically controlled brake unit

Vehicles without Mazda M Hybrid:

•  CAN communication: communication error to DSC HU/CM

Detection condition

Vehicles with Mazda M Hybrid:

•  Communication error between the PCM and electronically controlled brake unit continues for 5 s or more.

Vehicles without Mazda M Hybrid:

•  Communication error between the PCM and DSC HU/CM continues for 5 s or more.

Fail-safe

•  Inhibits the DSC control.

•  Inhibits engine-stop by operating the i-stop function. (With i-stop system)

Possible cause

Vehicles with Mazda M Hybrid:

•  CAN communication line malfunction between PCM and electronically controlled brake unit

•  Electronically controlled brake unit malfunction

•  PCM malfunction

Vehicles without Mazda M Hybrid:

•  CAN communication line malfunction between PCM and DSC HU/CM

•  DSC HU/CM malfunction

•  PCM malfunction

System wiring diagram

•  Not applicable

Connector diagram

•  Not applicable

System malfunction location	Vehicles with Mazda M Hybrid: • CAN communication: communication error to electronically controlled brake unit Vehicles without Mazda M Hybrid: • CAN communication: communication error to DSC HU/CM
Detection condition	Vehicles with Mazda M Hybrid: • Communication error between the PCM and electronically controlled brake unit continues for 5 s or more. Vehicles without Mazda M Hybrid: • Communication error between the PCM and DSC HU/CM continues for 5 s or more.
Fail-safe	• Inhibits the DSC control. • Inhibits engine-stop by operating the i-stop function. (With i-stop system)
Possible cause	Vehicles with Mazda M Hybrid: • CAN communication line malfunction between PCM and electronically controlled brake unit • Electronically controlled brake unit malfunction • PCM malfunction Vehicles without Mazda M Hybrid: • CAN communication line malfunction between PCM and DSC HU/CM • DSC HU/CM malfunction • PCM malfunction
System wiring diagram	• Not applicable
Connector diagram	• Not applicable

Diagnostic Procedure

• Inspect according to the diagnostic procedure in ON-BOARD DIAGNOSTIC [MULTIPLEX COMMUNICATION SYSTEM]. (See CONTROLLER AREA NETWORK (CAN) MALFUNCTION DIAGNOSIS FLOW [(E)].)