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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 line-to-line short in CAN bus (Engine control computer)
    1. Disconnect the battery ground terminal.
    2. Disconnect the vehicle wiring harness connector A33 from the engine control computer.
    3. Measure the resistance between the terminals.
      RESISTANCE

      Inspection terminals (Terminal symbol) Inspection conditions Standard value
      A33-19 - A33-18 Disconnection of the battery ground terminal 114 to 126 Ω

      NG: Go to Step 2

      Fig 1: Identifying Engine Control Computer Connector Terminals A33-18 And A33-19
      G08552974Courtesy of SUBARU OF AMERICA, INC.

      OK: Replacement of the engine control computer (Refer to REMOVAL )

  2. Check for line-to-line short in CAN bus (Brake actuator assembly)
    1. Reconnect the vehicle wiring harness connector A33 to the engine control computer.
    2. Disconnect the vehicle harness connector A5 from the brake actuator assembly.
    3. Measure the resistance between the terminals.
      RESISTANCE

      Inspection terminals (Terminal symbol) Inspection conditions Standard value
      A5-26 - A5-14 Disconnection of the battery ground terminal 114 to 126 Ω

      NG: Go to Step 3

      Fig 2: Identifying Brake Actuator Assembly Connector Terminals A5-14 And A5-26
      G08552975Courtesy of SUBARU OF AMERICA, INC.

      OK: Replace the brake actuator assembly (Refer to REMOVAL )

  3. Check for line-to-line short in CAN bus (Wiring harness connector (CAN J/C2))
    1. Reconnect the vehicle wiring harness connector A5 to the brake actuator assembly.
    2. Disconnect the vehicle harness connector D43 from the wiring harness connector (CAN J/C2).
    3. Measure the resistance between the terminals.
      Fig 3: Identifying Wiring Harness Connector (CAN J/C2) Terminals
      G08552976Courtesy of SUBARU OF AMERICA, INC.
      RESISTANCE

      Inspection terminals (Terminal symbol) Inspection conditions Standard value Connecting to
      D43-1 - D43-12 Disconnection of the battery ground terminal 114 to 126 Ω Wiring harness connector (CAN J/C1)
      D43-2 - D43-13 Disconnection of the battery ground terminal 200 Ωor more Combination meter assembly
      D43-3 - D43-14 Disconnection of the battery ground terminal 200 Ωor more Main body ECM (Multiplex network body computer)
      D43-4 - D43-15 Disconnection of the battery ground terminal 200 Ωor more Collation ECM (Smart key computer assembly)
      D43-5 - D43-16 Disconnection of the battery ground terminal 1 M Ωor more Data link connector
      D43-6 - D43-17 Disconnection of the battery ground terminal 200 Ωor more Spiral cable sub-assembly (with sensor)
      D43-8 - D43-19 Disconnection of the battery ground terminal 200 Ωor more Airbag sensor assembly
      D43-9 - D43-20 Disconnection of the battery ground terminal 114 to 126 Ω Engine control computer
      D43-10 - D43-21 Disconnection of the battery ground terminal 200 Ωor more Air conditioner amplifier assembly
      CRITERIA

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

      B: Go to Step 4

      C: Go to Step  6

      D: Go to Step  5

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

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

  4. Check for line-to-line short in CAN bus (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 terminals.
      RESISTANCE

      Inspection terminals (Terminal symbol) Inspection conditions Standard value Connecting to
      A17-5 - A17-16 Disconnection of the battery ground terminal 200 Ωor more Transmission control computer assembly
      A17-6 - A17-17 Disconnection of the battery ground terminal 114 to 126 Ω Skid control ECM (Brake actuator assembly)
      A17-7 - A17-18 Disconnection of the battery ground terminal 1 M Ωor more Wiring harness connector (CAN J/C2)
      A17-8 - A17-19 Disconnection of the battery ground terminal 200 Ωor more Power steering computer assembly
      Fig 4: Identifying Wiring Harness Connector (CAN J/C1) Terminals
      G08552977Courtesy of SUBARU OF AMERICA, INC.
      CRITERIA

      Result Go to
      OK (No line-to-line short circuit) A
      NG (Line-to-line short in the main line to the wiring harness connector (CAN J/C2)) B
      NG (Line-to-line short in the main line to the skid control ECM (Brake actuator assembly)) C
      NG (Line-to-line 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  7

      D: Go to Step 5

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

  5. Check for line-to-line short in CAN bus (ECM and sensor line)
    1. Reconnect all connections to the wiring harness connectors (CAN J/C1 and CAN J/C2).
    2. From the ECM and sensor relevant with line-to-line 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 line-to-line 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 (Terminal symbol) Inspection conditions Standard value
      D10-6 - D10-14 Disconnection of the battery ground terminal 57 to 63 Ω
      Fig 5: Identifying Data Link Connector Terminals
      G08552978Courtesy of SUBARU OF AMERICA, INC.
      NOTE:
      • If the resistance is less than 57 Ωwith the ECM and sensor connected (line-to-line short), there may be a ECM internal short.
      • 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 and sensor disconnected, repair or replace the wire harness and the connector in which line-to-line short has been detected.

      NG: Repair or replace the wiring harness

      OK: Replace the ECM/sensor

  6. Check for line-to-line 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 terminations.
      RESISTANCE

      Inspection terminals (Terminal symbol) Inspection conditions Standard value Connecting to
      D43-9 - D43-20 Battery terminal is disconnected 1 M Ωor more Engine control computer

      NG: Repair or replace the wiring harness and the connector where the line-to-line short was confirmed.

      OK: Replace the engine control computer

  7. Check for line-to-line short in CAN bus terminations (Brake actuator assembly)
    1. Disconnect the vehicle wiring harness connector A5 of the brake actuator assembly.
    2. Measure the resistance between terminations.
      RESISTANCE

      Inspection terminals (Terminal symbol) Inspection conditions Standard value Connecting to
      A17-6 - A17-17 Battery terminal is disconnected 1 M Ωor more Brake actuator assembly

      NG: Repair or replace the wiring harness and the connector where the line-to-line short was confirmed.

      OK: Replace the brake actuator assembly

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