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Inspection steps

WARNING: This page is about a different car, the 2014 Subaru BRZ. However, it is still accessible from the selected car via links, so may be relevant.
CAUTION:
  • Before measuring the resistance of CAN bus, turn the ignition OFF and leave the vehicle as is for at least one minute without operating keys, switches, and doors. Disconnect the battery and wait for another one minute or more.
  • If DTC related with CAN communication system is output, always start the troubleshooting according to the procedure described in "How to troubleshoot". (Refer to HOW TO TROUBLESHOOT  )
  • When the repair is complete, follow DTC check procedure to confirm the same DTC does not recur.

    DTC check procedure: Wait 60 seconds or more after IG ON, then drive the vehicle at 15 km/h or more for at least one second.

  • After turning the ignition switch to OFF, you may have to wait for a while before disconnecting the battery terminals. Check appropriate precautions for battery terminal disconnection before proceeding. (Refer to WORKING PRECAUTIONS AND NOTES )
NOTE:
  • Before disconnecting a connector, check for loose or unplugged connection by pushing back the connector case.
  • After disconnecting the connector, make sure that its terminal and the case have no damage, deformation, or corrosion.
  1. Check for CAN bus line short to GND (Wiring harness connector (CAN J/C2))
    1. Reconnect the vehicle wiring harness connectors: A5 to the brake actuator assembly and A33 to the engine control computer.
    2. Disconnect the vehicle harness connector D43 from the wiring harness connector (CAN J/C2).
    3. Measure the resistance between the terminal and GND.
      RESISTANCE

      Inspection terminals Inspection conditions Standard value Connecting to
      D43-1 - GND Disconnection of the battery ground terminal 200 Ωor more Wiring harness connector (CAN J/C1)
      D43-12 - GND
      D43-2 - GND Disconnection of the battery ground terminal 200 Ωor more Combination meter assembly
      D43-13 - GND
      D43-3 - GND Disconnection of the battery ground terminal 200 Ωor more Main body ECM (Multiplex network body computer)
      D43-14 - GND
      D43-4 - GND Disconnection of the battery ground terminal 200 Ωor more Collation ECM (Smart key computer assembly)
      D43-15 - GND
      D43-5 - GND Disconnection of the battery ground terminal 200 Ωor more Data link connector
      D43-16 - GND
      D43-6 - GND Disconnection of the battery ground terminal 200 Ωor more Spiral cable sub-assembly (with sensor)
      D43-17 - GND
      D43-8 - GND Disconnection of the battery ground terminal 200 Ωor more Airbag sensor assembly
      D43-19 - GND
      D43-9 - GND Disconnection of the battery ground terminal 200 Ωor more Engine control computer
      D43-20 - GND
      D43-10 - GND Disconnection of the battery ground terminal 200 Ωor more Air conditioner amplifier assembly
      D43-21 - GND
      Fig 1: Identifying Wiring Harness Connector (CAN J/C2) Terminals
      G08552986Courtesy of SUBARU OF AMERICA, INC.
      CRITERIA

      Result Go to
      OK (No short to ground) A
      NG (Ground short in the main line to the wiring harness connector (CAN J/C1)) B
      NG (Ground short in the main line to the engine control computer) C
      NG (Ground short in the line to ECM and sensor) D
      NG (Ground short in the sub-line to the data link connector) E

      B: Go to Step 2

      C: Go to Step  5

      D: Go to Step  3

      E: Repair or replace CAN bus sub-line or connector

      A: Replace the wiring harness connector (CAN J/C2)

  2. Check for CAN bus line short to GND (Wiring harness connector (CAN J/C1))
    1. Disconnect the vehicle harness connector A17 from the wiring harness connector (CAN J/C1).
    2. Measure the resistance between the terminal and GND.
      RESISTANCE

      Inspection terminals Inspection conditions Standard value Connecting to
      A17-5 - GND Disconnection of the battery ground terminal 200 Ωor more Transmission control computer assembly
      A17-16 - GND
      A17-6 - GND Disconnection of the battery ground terminal 200 Ωor more Skid control ECM (Brake actuator assembly)
      A17-17 - GND
      A17-7 - GND Disconnection of the battery ground terminal 200 Ωor more Wiring harness connector (CAN J/C2)
      A17-18 - GND
      A17-8 - GND Disconnection of the battery ground terminal 200 Ωor more Power steering computer assembly
      A17-19 - GND
      Fig 2: Identifying Wiring Harness Connector (CAN J/C1) Terminals
      G08552987Courtesy of SUBARU OF AMERICA, INC.
      CRITERIA

      Result Go to
      OK (No short to ground) A
      NG (Ground short in the main line to the wiring harness connector (CAN J/C2)) B
      NG (Ground short in the main line to the skid control ECM (Brake actuator assembly)) C
      NG (Ground short in the line to ECM) D

      B: Repair or replace CAN bus main line or connector (Wiring harness connector (CAN J/C2) - Wiring harness connector (CAN J/C1))

      C: Go to Step  4

      D: Go to Step 3

      A: Replace the wiring harness connector (CAN J/C1)

  3. Check for CAN bus line short to GND (ECM/sensor)
    1. Reconnect all connections to the wiring harness connectors (CAN J/C1 and CAN J/C2).
    2. From the ECM and sensor relevant with GND short circuit, disconnect the connectors with CAN-H and CAN-L terminals. (Refer to ECM TERMINAL ARRANGEMENT  for ECM terminal arrangement)
      NOTE: In case of more than one GND short circuit, disconnect all connectors including CANH and CANL terminals of the ECM and sensor.
    3. Measure the resistance between the terminals.
      RESISTANCE

      Inspection terminals Inspection conditions Standard value
      D10-6 - GND Disconnection of the battery ground terminal 200 Ωor more
      D10-14 - GND
      Fig 3: Identifying Data Link Connector Terminals
      G08552988Courtesy of SUBARU OF AMERICA, INC.
      NOTE:
      • If the resistance returns to normal with the ECM and sensor disconnected, there may be an internal short within the ECM and sensor.
      • When more than one ECM or sensor is disconnected, reconnect the part one by one to check the resistance. If an ECM or sensor shows an abnormal value, replace it. After that, reconnect all ECMs and sensors to check if the resistance returns to normal.
      • If the resistance does not return to normal with the ECM/sensor disconnected, repair or replace the wire harness and connector in which GND short has been detected.

      NG: Repair or replace the wiring harness

      OK: Replace the ECM/sensor

  4. Check for GND short in CAN bus termination (Brake actuator assembly)
    1. Disconnect the vehicle wiring harness connector A5 of the brake actuator assembly.
    2. Measure the resistance between the terminal and GND.
      RESISTANCE

      Inspection terminals Inspection conditions Standard value Connecting to
      A17-6 - GND Disconnection of the battery ground terminal 200 Ωor more Brake actuator assembly
      A17-17 - GND

      NG: Repair or replace the wiring harness and the connector in which GND short has been detected

      OK: Replace the brake actuator assembly

  5. Check for GND short in CAN bus termination (Engine control computer)
    1. Disconnect the vehicle wiring harness connector A33 from the engine control computer.
    2. Measure the resistance between the terminal and GND.
      RESISTANCE

      Inspection terminals Inspection conditions Standard value Connecting to
      D43-9 - GND Disconnection of the battery ground terminal 200 Ωor more Engine control computer
      D43-20 - GND

      NG: Repair or replace the wiring harness and the connector in which GND short has been detected

      OK: Replace the engine control computer

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