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Short in CAN Bus Lines: Procedure

WARNING: This page is about a different car, the 2009 Lexus IS 350 and 2009 Lexus IS 250. However, it is still accessible from the selected car via links, so may be relevant.
  1. CHECK FOR SHORT IN CAN BUS WIRES (DLC3 BRANCH LINE) 
    1. Turn the engine switch off.
    2. Disconnect the DLC3 branch line connector (J8) from the CAN LH J/C B side (w/o earth terminal).
      Fig 1: Identifying CAN LH J/C B Side (w/o earth terminal)
      GTY138099Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      NOTE:
      • Before disconnecting the connector, make a note of where it is connected.
      • Reconnect the connector to its original position.
    3. Measure the resistance according to the value(s) in the table below.
      Fig 2: Identifying DLC3 Connector Terminals
      GTY112667Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

      Standard Resistance

      Tester Connection Condition Specified Condition
      J21-6 (CANH) - J21-14 (CANL) Engine switch off 1 MΩ or higher

    NG → REPAIR OR REPLACE DLC3 BRANCH WIRE OR CONNECTOR 

    OK: Go to next step 

  2. RECONNECT CONNECTOR 
    1. Reconnect the DLC3 branch line connector (J8) to the CAN LH J/C B side (w/o earth terminal).

    NEXT: Go to next step 

  3. CHECK FOR SHORT IN CAN BUS WIRES (BRANCH LINE) 
    1. Connect the probes of an ohmmeter to terminals 6 (CANH) and 14 (CANL) of the DLC3.
      Fig 3: Identifying DLC3 Connector Terminal
      GTY135146Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    2. While observing the resistance value shown on the tester, disconnect connectors J1, J3, J4, J5, J6, J9, J82 and J86 from the CAN LH J/C or CAN RH J/C one by one until the resistance becomes normal (between 54 and 69 Ω).

      HINT: 

      Disconnect the branch line connectors other than those of the DLC3.

      Fig 4: Identifying CAN LH J/C Connectors Wiring Diagram
      GTY126987Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      Fig 5: Identifying CAN LH J/C Terminals
      GTY140136Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      WIRING COLOR:

      CAN LH J/C A Side (w/ Earth Terminal) Code Color (CANH Side) Color (CANL Side)
      Steering angle sensor J1 P W
      ECM J2 B W
      Seat belt control ECU
      (w/ Pre-collision system)      		 J3 V W
      Center airbag sensor J4 R W
      WIRING COLOR:

      CAN LH J/C B Side (w/o Earth Terminal) Code Color (CANH Side) Color (CANL Side)
      Yaw rate sensor J5 P W
      Skid control ECU J6 R W
      CAN main bus line (bus line connecting CAN LH J/C and CAN RH J/C) J7 B W
      DLC3 J8 G W
      Distance control ECU
      (w/ Dynamic radar cruise control system)      		 J9 GR W
      Fig 6: Identifying CAN RH J/C Terminals
      GTY139343Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      WIRING COLOR:

      CAN RH J/C A Side (w/ Earth Terminal) Code Color (CANH Side) Color (CANL Side)
      CAN main bus line (bus line connecting CAN RH J/C and CAN LH J/C) J81 B W
      Power steering ECU J82 P W
      WIRING COLOR:

      CAN RH J/C B Side (w/o Earth Terminal) Code Color (CANH Side) Color (CANL Side)
      Gateway ECU J84 B W
      4WD control ECU (for 4WD) J86 V W
      NOTE:

      Do not reconnect the disconnected connectors until this inspection is complete because there may be a short in 2 or more branch lines.

      Result

      Symptom Proceed to
      The resistance is still below 54 Ω when all the specified connectors are disconnected. (There are no shorts in the branch lines.) A
      The resistance becomes normal (between 54 and 69 Ω) when a connector is disconnected. (There is a short in one or more of the branch lines.) B
    3. When there is a short in one or more of the branch lines:
      1. Reconnect all of the connectors to the CAN J/C, except for the one that was disconnected last (the short-circuited bus line). Check that the resistance shown on the tester is normal (between 54 and 69 Ω) to confirm that there is a short in the one branch line only.

        HINT: 

        • The connectors connected to the CAN J/C can be distinguished according to the color of the communication bus lines and the shape of the connectors.
        • Reconnecting the connectors to non-specified positions on the CAN J/C does not affect system operation. However, it is preferred to reconnect the connectors to their specified positions to avoid negative effects on the wiring such as tension on the wiring harnesses, and to make future maintenance easier.

    B → See step   9 

    A: Go to next step 

  4. CHECK FOR SHORT IN CAN BUS WIRES (GATEWAY ECU MAIN BUS LINE) 
    1. Disconnect the gateway ECU main bus line connector (J84) from the CAN RH J/C B side (w/o earth terminal).
      Fig 7: Identifying Gateway ECU Main Bus Line Connector
      GTY137489Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      NOTE:
      • Before disconnecting the connector, make a note of where it is connected.
      • Reconnect the connector to its original position.
    2. Measure the resistance according to the value(s) in the table below.
      Fig 8: Identifying DLC3 Connector Terminal
      GTY135146Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

      Standard Resistance

      Tester Connection Condition Specified Condition
      J21-6 (CANH) - J21-14 (CANL) Engine switch off 108 to 132 Ω

      Result

      Symptom Proceed to
      The resistance is still below 54 Ω when the gateway ECU connector is disconnected. (There are no shorts in the gateway ECU main bus lines.) A
      The resistance falls within the specified range (between 108 and 132 Ω) (either of the terminating resistances is normal) when the gateway ECU connector is disconnected. (There is a short in the gateway ECU main bus lines.) B

    B → See step   11 

    A: Go to next step 

  5. CHECK FOR SHORT IN CAN BUS WIRES (ECM MAIN BUS LINE) 
    1. Disconnect the ECM main bus line connector (J2) from the CAN LH J/C A side (w/ earth terminal).
      Fig 9: Identifying CAN LH J/C A side (w/ earth terminal)
      GTY124218Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      NOTE:
      • Before disconnecting the connector, make a note of where it is connected.
      • Reconnect the connector to its original position.
    2. Measure the resistance according to the value(s) in the table below.
      Fig 10: Identifying DLC3 Connector Terminal
      GTY135146Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

      Standard Resistance

      Tester Connection Condition Specified Condition
      J21-6 (CANH) - J21-14 (CANL) Engine switch off 1 MΩ or higher

      HINT: 

      Measure the resistance with the gateway ECU main bus line connector (J84) disconnected.

      Result

      Symptom Proceed to
      The resistance is still below 1 MΩ when the ECM connector is disconnected. (There are no shorts in the ECM main bus lines.) A
      The resistance becomes 1 MΩ or more when the ECM connector is disconnected. (There is a short in the ECM main bus lines.) B

    B → See step   13 

    A: Go to next step 

  6. CHECK CAN LH J/C 
    1. Disconnect the CAN main bus line connector (J7) from the CAN LH J/C B side (w/o earth terminal).
      Fig 11: Identifying CAN Main Bus Line Connector (J7)
      GTY137490Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      NOTE:
      • Before disconnecting the connector, make a note of where it is connected.
      • Reconnect the connector to its original position.
    2. Measure the resistance according to the value(s) in the table below.
      Fig 12: Identifying DLC3 Connector Terminal
      GTY135146Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

      Standard Resistance

      Tester Connection Condition Specified Condition
      J21-6 (CANH) - J21-14 (CANL) Engine switch off 1 MΩ or higher

    NG → REPLACE CAN LH J/C 

    OK: Go to next step 

  7. RECONNECT CONNECTOR 
    1. Reconnect the CAN main bus line connector (J7) to the CAN LH J/C B side (w/o earth terminal).

    NEXT: Go to next step 

  8. CHECK CAN RH J/C 
    1. Disconnect the CAN main bus line connector (J81) from the CAN RH J/C A side (w/ earth terminal).
      Fig 13: Identifying CAN Main Bus Line Connector (J81)
      GTY124219Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      NOTE:
      • Before disconnecting the connector, make a note of where it is connected.
      • Reconnect the connector to its original position.
    2. Measure the resistance according to the value(s) in the table below.
      Fig 14: Identifying DLC3 Connector Terminal
      GTY135146Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

      Standard Resistance

      Tester Connection Condition Specified Condition
      J21-6 (CANH) - J21-14 (CANL) Engine switch off 1 MΩ or higher

    OK → REPLACE CAN RH J/C 

    NG → REPAIR OR REPLACE CAN BUS MAIN WIRE (CAN LH J/C - CAN RH J/C) 

  9. RECONNECT CONNECTOR 
    1. Reconnect the connector for the short-circuited branch line to the CAN J/C (the connector that caused the bus line resistance to become normal (between 54 and 69 Ω) when it was disconnected).

    NEXT: Go to next step 

  10. CHECK FOR SHORT IN CAN BUS WIRES 
    1. Disconnect the connector that includes terminals CANH and CANL from the ECU (or sensor) to which the short-circuited branch line is connected.. Refer to TERMINALS OF ECU 
      Fig 15: Identifying DLC3 Connector Terminal
      GTY135146Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    2. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      J21-6 (CANH) - J21-14 (CANL) Engine switch off 1 MΩ or higher

      HINT: 

      If the resistance becomes normal (between 54 and 69 Ω) when the connector is disconnected from the ECU (or sensor), there may be a short in the ECU (or sensor).

    NG → REPAIR OR REPLACE CORRESPONDING ECU OR SENSOR BRANCH WIRE OR CONNECTOR 

    OK → REPLACE CORRESPONDING ECU OR SENSOR 

  11. RECONNECT CONNECTOR 
    1. Reconnect the gateway ECU main bus line connector (J84) to the CAN RH J/C B side (w/o earth terminal).

    NEXT: Go to next step 

  12. CHECK FOR SHORT IN CAN BUS WIRES (GATEWAY ECU) 
    1. Disconnect the gateway ECU connector (J76).
      Fig 16: Identifying DLC3 Connector Terminal
      GTY135146Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    2. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      J21-6 (CANH) - J21-14 (CANL) Engine switch off 108 to 132 Ω

      HINT: 

      If the resistance becomes normal (between 108 to 132 Ω) when the connector is disconnected, there may be a short in the gateway ECU.

    NG → REPAIR OR REPLACE CAN BUS MAIN WIRE (GATEWAY ECU MAIN BUS LINE) 

    OK → REPLACE GATEWAY ECU 

  13. RECONNECT CONNECTOR 
    1. Reconnect the ECM main bus line connector (J2) to the CAN LH J/C A side (w/ earth terminal).

    NEXT: Go to next step 

  14. CHECK FOR SHORT IN CAN BUS WIRES (ECM) 
    1. Disconnect the ECM connector (A5).
      Fig 17: Identifying DLC3 Connector Terminal
      GTY135146Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    2. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      J21-6 (CANH) - J21-14 (CANL) Engine switch off 1 MΩ or higher

      HINT: 

      • Measure the resistance with the gateway ECU main bus line connector (J84) disconnected.
      • If the resistance changes to 1 MΩ or more when the connector is disconnected, there may be a short in the ECM.

    NG → REPAIR OR REPLACE CAN BUS MAIN WIRE (ECM MAIN BUS LINE) 

    OK → REPLACE ECM 

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