CAN COMMUNICATION SYSTEM Check CAN Bus Lines for Short Circuit (LHD Models)

DESCRIPTION

There may be a short circuit between the V bus main lines and/or CAN branch lines when the resistance between terminals 6 (CANH) and 14 (CANL) of the DLC3 is below 57 Ω.

Symptom Trouble Area
Resistance between terminals 6 (CANH) and 14 (CANL) of DLC3 is below 57 Ω.

  • Short in CAN main bus line

  • Short in CAN branch line

  • Main body ECU (network gateway ECU)

  • Combination meter assembly

  • Certification ECU (smart key ECU assembly)*1

  • ECM

  • TCM*2

  • Skid control ECU

  • Steering angle sensor (spiral cable sub-assembly)

  • Power steering ECU assembly

  • Air conditioning control assembly*3

  • Air bag ECU assembly

  • CAN No. 1 junction connector

  • CAN No. 2 junction connector

*1: w/ Entry and Start System

*2: for Automatic Transmission System

*3: for Automatic Air Conditioning System

WIRING DIAGRAM

B008BFEE02
B008BI9E02

CAUTION / NOTICE / HINT

Note


  • Before measuring the resistance of the CAN bus, turn the ignition switch off and leave the vehicle for 1 minute or more without operating the key, switches or opening or closing the doors. After that, disconnect the cable from the negative (-) battery terminal and leave the vehicle for 1 minute or more before measuring the resistance.

  • After turning the ignition switch off, waiting time may be required before disconnecting the cable from the negative (-) battery terminal. Therefore, make sure to read the disconnecting the cable from the negative (-) battery terminal notices before proceeding with work Click here.

  • Because the order of diagnosis is important to allow correct diagnosis, make sure to begin troubleshooting using How to Proceed with Troubleshooting when CAN communication system related DTCs are output Click here.

  • After performing repairs, perform the DTC check procedure and confirm that the DTCs are not output again.

  • DTC check procedure: Turn the ignition switch to ON, wait at least 60 seconds,

  • After the repair, perform CAN Bus Check and check that all the ECUs and sensors connected to the CAN communication system are displayed Click here.

Tech Tips


  • Operating the ignition switch, any other switches or a door triggers related ECU and sensor communication on the CAN. This communication will cause the resistance value to change.

  • Even after DTCs are cleared, if a DTC is stored again after driving the vehicle for a while, the malfunction may be occurring due to vibration of the vehicle. In such a case, wiggling the ECUs or wire harness while performing the inspection below may help determine the cause of the malfunction.

PROCEDURE


  1. CHECK FOR SHORT IN CAN BUS LINES (ECM)


    1. Disconnect the cable from the negative (-) battery terminal.

    2. B008BFBE02
      Text in Illustration
      *a

      Front view of wire harness connector

      (to ECM)

      Disconnect the A33 ECM connector.

    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance
      Tester Connection Condition Specified Condition
      A33-19 (CANH) - A33-18 (CANL) Cable disconnected from negative (-) battery terminal 114 to 126 Ω

    OK

    REPLACE ECM Click here

    NG

  2. CHECK FOR SHORT IN CAN BUS LINES (SKID CONTROL ECU (BRAKE ACTUATOR ASSEMBLY))


    1. Reconnect the A33 ECM connector.

    2. B008BC3E04
      Text in Illustration
      *a

      Front view of wire harness connector

      (to Skid Control ECU (Brake Actuator Assembly))

      Disconnect the A5 skid control ECU (brake actuator assembly) connector.

    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance
      Tester Connection Condition Specified Condition
      A5-26 (CANH) - A5-14 (CANL) Cable disconnected from negative (-) battery terminal 114 to 126 Ω

    OK

    REPLACE SKID CONTROL ECU Click here

    NG

  3. CHECK FOR SHORT IN CAN BUS LINES (CAN NO. 2 J/C)


    1. Reconnect the A5 skid control ECU (brake actuator assembly) connector.

    2. B008BI0E04
      Text in Illustration
      *a

      Front view of wire harness connector

      (to CAN No. 2 Junction Connector)
      *b to CAN No. 1 Junction Connector
      *c to Combination Meter Assembly
      *d to Main Body ECU (Network Gateway ECU)
      *e to Certification ECU (Smart Key ECU Assembly)
      *f to DLC3
      *g to Steering Angle Sensor (Spiral Cable Sub-assembly)
      *h to PSP (Option Connector)
      *i to Air Bag ECU Assembly
      *j to ECM
      *k to Air Conditioning Control Assembly

      Disconnect the wire harness connector from the D43 CAN No. 2 junction connector.

    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance
      Tester Connection Condition Specified Condition Connected to
      D43-1 - D43-12 Cable disconnected from negative (-) battery terminal 114 to 126 Ω CAN No. 1 junction connector
      D43-2 - D43-13 Cable disconnected from negative (-) battery terminal 200 Ω or higher Combination meter assembly
      D43-3 - D43-14 Cable disconnected from negative (-) battery terminal 200 Ω or higher Main body ECU (network gateway ECU)
      D43-4 - D43-15 Cable disconnected from negative (-) battery terminal 200 Ω or higher Certification ECU (smart key ECU assembly)
      D43-5 - D43-16 Cable disconnected from negative (-) battery terminal 1 MΩ or higher DLC3
      D43-6 - D43-17 Cable disconnected from negative (-) battery terminal 200 Ω or higher Steering angle sensor (spiral cable sub-assembly)
      D43-7 - D43-18 Cable disconnected from negative (-) battery terminal 1 MΩ or higher PSP (option connector)
      D43-8 - D43-19 Cable disconnected from negative (-) battery terminal 200 Ω or higher Air bag ECU assembly
      D43-9 - D43-20 Cable disconnected from negative (-) battery terminal 114 to 126 Ω ECM
      D43-10 - D43-21 Cable disconnected from negative (-) battery terminal 200 Ω or higher Air conditioning control assembly
      Result
      Result Proceed to
      OK A
      NG (CAN No. 1 junction connector main line) B
      NG (ECM main line) C
      NG (ECU or sensor branch line) D
      NG (DLC3 branch line or PSP (option connector) branch line) E

    A

    REPLACE CAN NO. 2 JUNCTION CONNECTOR

    C

    REPAIR OR REPLACE CAN MAIN BUS LINE OR CONNECTOR (CAN NO. 2 J/C - ECM)

    D

    CHECK FOR SHORT IN CONNECTED COMPONENT (ECU, SENSOR) Click here

    E

    REPAIR OR REPLACE CAN BRANCH LINE CONNECTED TO DLC3 OR PSP (OPTION CONNECTOR)

    B

  4. CHECK FOR SHORT IN CAN BUS LINES (CAN NO. 1 J/C)


    1. B008BF8E02
      Text in Illustration
      *a

      Front view of wire harness connector

      (to CAN No. 1 Junction Connector)
      *b to TCM
      *c to Skid Control ECU (Brake Actuator Assembly)
      *d to CAN No. 2 Junction Connector
      *e to Power Steering ECU Assembly

      Disconnect the wire harness connector from the A17 CAN No. 1 junction connector.

    2. Measure the resistance according to the value(s) in the table below.

      Standard Resistance
      Tester Connection Condition Specified Condition Connected to
      A17-5 - A17-16 Cable disconnected from negative (-) battery terminal 200 Ω or higher TCM
      A17-6 - A17-17 Cable disconnected from negative (-) battery terminal 114 to 126 Ω Skid control ECU (brake actuator assembly)
      A17-7 - A17-18 Cable disconnected from negative (-) battery terminal 1 MΩ or higher CAN No. 2 junction connector
      A17-8 - A17-19 Cable disconnected from negative (-) battery terminal 200 Ω or higher Power steering ECU assembly
      Result
      Result Proceed to
      OK A
      NG (CAN No. 2 junction connector main line) B
      NG (skid control ECU (brake actuator assembly) main line) C
      NG (ECU or sensor branch line) D

    A

    REPLACE CAN NO. 1 JUNCTION CONNECTOR

    B

    REPAIR OR REPLACE CAN MAIN BUS LINE OR CONNECTOR (CAN NO. 2 J/C - CAN NO. 1 J/C)

    C

    REPAIR OR REPLACE CAN MAIN BUS LINE OR CONNECTOR (CAN NO. 1 J/C - SKID CONTROL ECU (BRAKE ACTUATOR ASSEMBLY))

    D

  5. CHECK FOR SHORT IN CONNECTED COMPONENT (ECU, SENSOR)


    1. Reconnect all the wire harness connectors (the A17 CAN No. 1 junction connector and D43 CAN No. 2 junction connector).

    2. Disconnect the connector that includes terminals CANH and CANL from the ECU (or sensor) to which the short circuited branch line is connected Click here.

    3. B008BG9E04
      Text in Illustration
      *1 DLC3

      Measure the resistance according to the value(s) in the table below.

      Standard Resistance
      Tester Connection Condition Specified Condition
      D10-6 (CANH) - D10-14 (CANL) Cable disconnected from negative (-) battery terminal 57 to 63 Ω

      Tech Tips


      • If the resistance becomes normal (between 57 and 63 Ω) when the connector is disconnected from the ECU (or sensor), there may be a short in the ECU (or sensor).

      • If the resistance does not become normal (between 57 and 63 Ω) when the connector is disconnected from the ECU (or sensor), repair or replace the short circuited branch line or connector.


    OK

    REPLACE CORRESPONDING ECU OR SENSOR

    NG

    REPAIR OR REPLACE CORRESPONDING ECU OR SENSOR BUS LINE OR CONNECTOR