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Inspection steps

WARNING: This page is about a different car, the 2018 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. Checking for CAN bus line short to GND (Wiring harness connector (CAN J/C2))
    G12589143Courtesy of SUBARU OF AMERICA, INC.
    1. Reconnect the vehicle wiring harness connectors: A5 to the brake actuator ASSY 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.
    STANDARD VALUE SPECIFICATION - 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 ASSY
    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 ASSY)
    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-ASSY (with sensor)
    D43-17 - GND
    D43-8 - GND Disconnection of the battery ground terminal 200 Ωor more Airbag sensor ASSY
    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 ASSY
    D43-21 - GND
    RESULT DESCRIPTION - 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 replacement of CAN bus sub-line or connector

    A: Go to next step

    Replacement of the wiring harness connector (CAN J/C2)

  2. Checking for CAN bus line short to GND (Wiring harness connector (CAN J/C1))
    G12589144Courtesy of SUBARU OF AMERICA, INC.
    1. Disconnect the vehicle harness connector A17 from the wiring harness connector (CAN J/C1).
    2. Measure the resistance between the terminal and GND.
    STANDARD VALUE SPECIFICATION - RESISTANCE

    Inspection terminals Inspection conditions Standard value Connecting to
    A17-5 - GND Disconnection of the battery ground terminal 200 Ωor more Transmission control computer ASSY
    A17-16 - GND
    A17-6 - GND Disconnection of the battery ground terminal 200 Ωor more Skid control ECM (Brake actuator ASSY)
    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 ASSY
    A17-19 - GND
    RESULT DESCRIPTION - 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 ASSY)) C
    NG (Ground short in the line to ECM) D

    B: Repair or replacement of 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: Go to next step

    Replacement of the wiring harness connector (CAN J/C1)

  3. Checking for CAN bus line short to GND (ECM/sensor)
    G12589145Courtesy of SUBARU OF AMERICA, INC.
    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 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.
    STANDARD VALUE SPECIFICATION - RESISTANCE

    Inspection terminals Inspection conditions Standard value
    D10-6 - GND Disconnection of the battery ground terminal 200 Ωor more
    D10-14 - GND
    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 replacement of the wiring harness

    OK: Go to next step

    Replacement of the ECM/sensor

  4. Checking for GND short in CAN bus termination (Brake actuator ASSY)
    1. Disconnect the vehicle wiring harness connector A5 of the brake actuator ASSY.
    2. Measure the resistance between the terminal and GND.
    STANDARD VALUE SPECIFICATION - RESISTANCE

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

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

    OK: Go to next step

    Replacement of the brake actuator ASSY

  5. Checking 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.
    STANDARD VALUE SPECIFICATION - 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 replacement of the wiring harness and the connector in which GND short has been detected

    OK: Go to next step

    Replacement of the engine control computer

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