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Home >> Subaru >> 2017 >> BRZ Limited, Automatic Trans >> Repair and Diagnosis >> Transmission >> Automatic Trans >> Automatic Transaxle (Diagnostics) >> Automatic transmission system >> DTC U0073, U0401, U0416, U0422, U0423: Control Module Communication Bus "A" Off, DTC Invalid Data Received From ECM/PCM "A" Invalid Data Received From Vehicle Dynamics Control Module, Invalid Data Received From Body Control Module, Invalid Data Received From Instrument Panel Cluster Control Module
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DTC U0073, U0401, U0416, U0422, U0423: Control Module Communication Bus "A" Off, DTC Invalid Data Received From ECM/PCM "A" Invalid Data Received From Vehicle Dynamics Control Module, Invalid Data Received From Body Control Module, Invalid Data Received From Instrument Panel Cluster Control Module

Circuit description

The transmission control computer ASSY sends/receives signals to/from ECMs via CAN communication.

NOTE:
  • Problems on the CAN bus (communication line) can be checked from the DLC3 connector. (Except when a DLC3 branch line is disconnected.)
  • Diagnostic codes related to CAN communication can be checked using SSM4.
  • Although DLC3 is connected to the CAN communication line, CAN communication cannot detect problems on the DLC3 branch lines.
DTC No. SAE/TCCS DTC detecting condition
  1. Diagnosis condition
  2. Abnormal status
  3. Abnormal period
  4. Others
 Inspection parts
U0073
  1. IG voltage remains at 9 V or larger for 1 second or more.
  2. Data cannot be sent/received.
  3. 500 ms
  4. trips
  • CAN system
U0401
  1. CAN bus is normal.
  2. Abnormal signal from engine control computer is received.
  3. times
  4. trips
  • CAN system
U0416
  1. CAN bus is normal.
  2. Abnormal signal from skid control computer (brake actuator ASSY) is received.
  3. times
  4. trips
  • CAN system
U0422
  1. CAN bus is normal.
  2. Abnormal signal from main body ECM (multiplex network body computer) is received.
  3. times
  4. trips
  • CAN system
U0423
  1. CAN bus is normal.
  2. Abnormal signal from combination meter ASSY is received.
  3. times
  4. trips
  • CAN system
MONITOR STRATEGY DESCRIPTION

Applicable diagnostic codes U0073: CAN failure A system bus off detection
U0401: Data error from engine
U0416: Data error from VDC
Required sensor/component U0073: TCM
U0401: TCM
U0406: Skid control ECM
Operation frequency Consecutive
Period 1 count
MIL operation Immediate
Operation order None

TYPICAL ENABLING CONDITIONS

TYPICAL ENABLING CONDITIONS DESCRIPTION

Battery voltage 9.0V or more
Above condition is established 1 second or more
TYPICAL ENABLING CONDITIONS DESCRIPTION

Battery voltage 9.0V or more
Above condition is established 1 second or more
CAN bus OFF (U0073) No defect
TYPICAL ENABLING CONDITIONS DESCRIPTION

Battery voltage 9.0V or more
Above condition is established 1 second or more
CAN bus OFF (U0073) No defect

TYPICAL MALFUNCTION THRESHOLDS

TYPICAL MALFUNCTION THRESHOLDS DESCRIPTION

CAN controller confirms the bus every 50 milliseconds, then the bus is turned OFF. 1 count or more
TYPICAL MALFUNCTION THRESHOLDS DESCRIPTION

The communication counter does not count up.
(Check the communication counter value every 10 milliseconds.)		 50 count
TYPICAL MALFUNCTION THRESHOLDS DESCRIPTION

The communication counter does not count up.
(Check the communication counter value every 10 milliseconds.)		 40 count

Inspection steps

  1. Read the diagnostic code
    1. Connect the SSM4 to the DLC3.
    2. Turn the ignition switch to ON.
    3. Read diagnostic codes according to SSM4 display. (Refer to Check list for interview )

    Next: To CAN communication system (Refer to How to troubleshoot )

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