CAN COMMUNICATION SYSTEM Check CAN Bus Line for Short to +B (LHD Models)

DESCRIPTION

There may be a short circuit between one of the CAN bus lines and +B when no resistance exists between terminals 6 (CANH) and 16 (BAT) or 14 (CANL) and 16 (BAT) of the DLC3.

Symptom Trouble Area
No resistance exists between terminals 6 (CANH) and 16 (BAT) or 14 (CANL) and 16 (BAT) of DLC3.

  • Short in CAN main bus line

  • Short in CAN branch line

  • Combination meter assembly

  • Power steering ECU with motor assembly

  • Main body ECU (Multiplex network body ECU)

  • Steering sensor

  • Airbag sensor assembly

  • ECM

  • Brake actuator assembly (Skid control ECU)

  • Air conditioning amplifier assembly

  • Certification ECU (Smart key ECU assembly)

  • Network gateway ECU*1

  • Multi-media module receiver assembly*2

  • Clearance warning ECU assembly

  • CAN junction connector LH1

  • CAN junction connector RH1

WIRING DIAGRAM

A01G45XE01
A01G56QE01

INSPECTION PROCEDURE

Note


  • Before measuring the resistance of the CAN bus, turn the engine 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 engine 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 engine switch on (IG), turn the blind spot monitor main switch on, wait at least 60 seconds and then drive the vehicle at a speed of 20 km/h (12 mph) or more for 5 minutes or more.

  • 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.

  • If the main body ECU (multiplex network body ECU) is replaced, refer to Service Bulletin.

Tech Tips


  • Operating the engine 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.

  • Connectors that connect to the CAN junction connector can be distinguished by the color of their CAN bus lines. When the connectors have been disconnected from the CAN junction connector, reconnecting the connectors to non-original positions on the CAN junction connector does not affect system performance. However, it is preferred to reconnect the connectors to their original positions to avoid negative effects on the wiring such as tension on the wiring harnesses, and to make future maintenance easier.

PROCEDURE


  1. CHECK FOR SHORT TO +B IN CAN BUS LINE (DLC3 BRANCH LINE)


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

    2. A01G49WE05
      Text in Illustration
      *a

      Rear view of wire harness connector

      (to CAN Junction Connector LH1)
      *b to DLC3

      Disconnect the H119 DLC3 branch line connector.

      Note


      • Before disconnecting the connector, make a note of where it is connected.

      • Reconnect the connector to its original position.

    3. A01G9KDE96
      Text in Illustration
      *1 DLC3

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      H29-6 (CANH) - H29-16 (BAT) Cable disconnected from negative (-) battery terminal 6 kΩ or higher
      H29-14 (CANL) - H29-16 (BAT) Cable disconnected from negative (-) battery terminal 6 kΩ or higher

    NG

    REPAIR OR REPLACE CAN BRANCH LINE CONNECTED TO DLC3

    OK

  2. CHECK FOR SHORT TO +B IN CAN BUS LINE


    1. Reconnect the H119 DLC3 branch line connector.

    2. A01G9KDE96
      Text in Illustration
      *1 DLC3

      Disconnect the connectors from the CAN junction connector LH1 and CAN junction connector RH1 one at a time.

      Tech Tips

      Disconnect the ECU and sensor connectors other than the DLC3 branch lines and CAN main bus lines between the CAN junction connector LH1 and CAN junction connector RH1.

    3. Using an ohmmeter, measure the resistance between terminals 6 (CANH) and 16 (BAT), and between terminals 14 (CANL) and 16 (BAT) of the DLC3 each time a connector is disconnected.

      A01G4VBE02
      Text in Illustration
      *A w/ Blind Spot Monitor System or Lane Departure Alert System *B w/ Navigation System
      *1 Steering Sensor *2 Main Body ECU (Multiplex Network Body ECU)
      *3 Airbag Sensor Assembly *4 DLC3
      *5 Combination Meter Assembly *6 Power Steering ECU with Motor Assembly
      *7 Brake Actuator Assembly (Skid Control ECU) *8 Air Conditioning Amplifier Assembly
      *9 ECM *10 Network Gateway ECU
      *11 Certification ECU (Smart Key ECU Assembly) *12 Clearance Warning ECU Assembly
      *13 Multi-media Module Receiver Assembly *14 CAN Junction Connector LH1
      *15 CAN Junction Connector RH1 - -
      A01G74LE01
      Text in Illustration
      *a

      Component without harness connected

      (CAN Junction Connector LH1)

      		 - -
      Wiring Color
      CAN Junction Connector LH1 Side Code Color (CANH Side) Color (CANL Side)
      Power steering ECU with motor assembly H133 B W
      CAN main bus line (bus line connecting CAN junction connector LH1 and CAN junction connector RH1) H116 R W
      Combination meter assembly H117 G W
      DLC3 H119 L W
      Airbag sensor assembly H134 Y W
      Main body ECU (Multiplex network body ECU) H118 V W
      Steering sensor H120 P W
      A01G8GHE10
      Text in Illustration
      *a

      Component without harness connected

      (CAN Junction Connector RH1)

      		 - -
      Wiring Color
      CAN Junction Connector RH1 Side Code Color (CANH Side) Color (CANL Side)
      Multi-media module receiver assembly*1 H128 BE W
      Clearance warning ECU assembly H132 P W
      Certification ECU (Smart key ECU assembly) H127 V W
      Network gateway ECU*2 H129 Y W
      ECM H125 L W
      Air conditioning amplifier assembly H123 G W
      CAN main bus line (bus line connecting CAN junction connector LH1and CAN junction connector RH1) H122 R W
      Brake actuator assembly (Skid control ECU) H126 B W

      • *1: w/ Navigation system

      • *2: w/ Blind spot monitor system or lane departure alert system

      Note

      Do not reconnect the disconnected connectors until this inspection is complete because there may be a short to +B in 2 or more CAN bus lines.

      Result
      Symptom Proceed to
      The resistance between terminals 6 (CANH) and 16 (BAT), or the resistance between 14 (CANL) and 16 (BAT) is still below 6 kΩ when all the specified connectors are disconnected from the CAN junction connector. (There is a short to +B in the CAN main bus lines between the CAN junction connector LH1 and CAN junction connector RH1.) A
      The resistance between terminals 6 (CANH) and 16 (BAT), or the resistance between 14 (CANL) and 16 (BAT) becomes normal (6 kΩ or more) when a connector is disconnected from the CAN junction connector. (There is a short to +B in one of the areas that relate to one or more of the disconnected bus lines.) B

    4. When there is a short to +B in one or more of the bus lines that connect to an ECU (or sensor):


      1. Reconnect all of the connectors to the CAN junction connector, except for the one that was disconnected last (the bus line that is shorted to +B). Check that the resistance shown on the tester is normal (6 kΩ or more) to confirm that there is a short to +B in the one bus line only.

        Tech Tips


        • Connectors that connect to the CAN junction connector can be distinguished by the color of their CAN bus lines.

        • Reconnecting the connectors to non-original positions on the CAN junction connector does not affect system performance. However, it is preferred to reconnect the connectors to their original positions to avoid negative effects on the wiring such as tension on the wiring harnesses, and to make future maintenance easier.

    5. When there is no short to +B in any of the bus lines that connect to the ECUs and sensors:


      1. With all the specified connectors for ECUs and sensors disconnected, proceed with the inspection of the CAN bus main lines between the CAN junction connector LH1 and CAN junction connector RH1.


    B

    CHECK FOR SHORT TO +B IN CAN BUS LINE (ECU, SENSOR) Click here

    A

  3. CHECK FOR SHORT TO +B IN CAN BUS LINE (CAN J/C LH1)


    1. A01G51SE05
      Text in Illustration
      *a

      Rear view of wire harness connector

      (to CAN Junction Connector LH1)
      *b to CAN Junction Connector RH1

      Disconnect the H116 CAN main bus line connector.

      Note


      • Before disconnecting the connector, make a note of where it is connected.

      • Reconnect the connector to its original position.

    2. A01G9KDE96
      Text in Illustration
      *1 DLC3

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      H29-6 (CANH) - H29-16 (BAT) Cable disconnected from negative (-) battery terminal 6 kΩ or higher
      H29-14 (CANL) - H29-16 (BAT) Cable disconnected from negative (-) battery terminal 6 kΩ or higher

    NG

    REPLACE CAN JUNCTION CONNECTOR LH1

    OK

  4. CHECK FOR SHORT TO +B IN CAN BUS LINE (CAN J/C LH1 - CAN J/C RH1)


    1. Reconnect the H116 CAN main bus line connector.

    2. A01G51SE06
      Text in Illustration
      *a

      Rear view of wire harness connector

      (to CAN Junction Connector RH1)
      *b to CAN Junction Connector LH1

      Disconnect the H122 CAN main bus line connector.

      Note


      • Before disconnecting the connector, make a note of where it is connected.

      • Reconnect the connector to its original position.

    3. A01G9KDE96
      Text in Illustration
      *1 DLC3

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      H29-6 (CANH) - H29-16 (BAT) Cable disconnected from negative (-) battery terminal 6 kΩ or higher
      H29-14 (CANL) - H29-16 (BAT) Cable disconnected from negative (-) battery terminal 6 kΩ or higher

    NG

    REPAIR OR REPLACE CAN MAIN BUS LINE (CAN J/C LH1 - CAN J/C RH1)

    OK

    REPLACE CAN JUNCTION CONNECTOR RH1

  5. CHECK FOR SHORT TO +B IN CAN BUS LINE (ECU, SENSOR)


    1. Reconnect the connector of the bus line that is shorted to +B to the CAN junction connector (the connector that caused the bus line resistance to change to 6 kΩ or more when it was disconnected).

    2. A01G9KDE96
      Text in Illustration
      *1 DLC3

      Disconnect the connector that includes the DLC3 connected CAN lines (such as CANH and CANL) from the ECU (or sensor) to which the bus line shorted to +B is connected Click here.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      H29-6 (CANH) - H29-16 (BAT) Cable disconnected from negative (-) battery terminal 6 kΩ or higher
      H29-14 (CANL) - H29-16 (BAT) Cable disconnected from negative (-) battery terminal 6 kΩ or higher

      Tech Tips

      If the resistance changes to 6 kΩ or higher 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 BUS LINE OR CONNECTOR

    OK

    REPLACE CORRESPONDING ECU OR SENSOR