CAN COMMUNICATION SYSTEM Check CAN Bus Line for Short to GND

DESCRIPTION

There may be a short circuit between one of the CAN bus lines and GND when there is no resistance between terminals 6 (CANH) and 4 (CG) or 14 (CANL) and 4 (CG) of the DLC3.

Symptom Trouble Area
No resistance exists between terminals 6 (CANH) and 4 (CG) or 14 (CANL) and 4 (CG) of DLC3.

  • Short to ground in CAN main bus line

  • Short to ground in CAN branch line

  • Power management control ECU

  • ECM

  • Main body ECU (Multiplex network body ECU)

  • Combination meter assembly

  • Brake booster with master cylinder assembly (Skid control ECU)

  • Steering sensor

  • Power steering ECU assembly

  • Airbag sensor assembly

  • Air conditioning amplifier assembly

  • Smart key ECU assembly (Certification ECU)

  • Navigation receiver assembly*1

  • Radio and display receiver assembly*2

  • Clearance warning ECU assembly*3

  • Tire pressure warning ECU and receiver*4

  • CAN junction LH connector

  • CAN junction RH connector

WIRING DIAGRAM

A01I2H9E02
A01I2IOE01

INSPECTION PROCEDURE

Note


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

  • After turning the power switch off, waiting time may be required before disconnecting the cable from the negative (-) auxiliary battery terminal. Therefore, make sure to read the disconnecting the cable from the negative (-) auxiliary 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 power switch on (IG), turn the cruise control main switch on, 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 11 seconds or more.

  • After the repair, perform the 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 power 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 wire harnesses, and to make future maintenance easier.

PROCEDURE


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


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

    2. A01I4Z8E01
      Text in Illustration
      *a

      Rear view of wire harness connector

      (to CAN Junction LH Connector)
      *b to DLC3

      Disconnect the I96 CAN junction LH connector.

      Note


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

      • Reconnect the connector to its original position.

    3. A01I5PBE49
      Text in Illustration
      *1 DLC3

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      I39-6 (CANH) - I39-4 (CG) Cable disconnected from negative (-) auxiliary battery terminal 200 Ω or higher
      I39-14 (CANL) - I39-4 (CG) Cable disconnected from negative (-) auxiliary battery terminal 200 Ω or higher

    NG

    REPAIR OR REPLACE CAN BRANCH LINE CONNECTED TO DLC3

    OK

  2. CHECK FOR SHORT TO GND IN CAN BUS LINE


    1. Reconnect the I96 CAN junction LH connector.

    2. A01I5PBE49
      Text in Illustration
      *1 DLC3

      Disconnect the connectors from the CAN junction LH connector and CAN junction RH connector 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 LH connector and CAN junction RH connector.

    3. Using an ohmmeter, measure the resistance between terminals 6 (CANH) and 4 (CG), and between terminals 14 (CANL) and 4 (CG) of the DLC3 each time a connector is disconnected.

      A01I5VYE02
      Text in Illustration
      *A w/ Intuitive Parking Assist System *B for Tire Pressure Warning System with Tire Inflation Pressure Display Function
      *C for Navigation Receiver Type *D for Radio and Display Type
      *1 Clearance Warning ECU Assembly *2 Tire Pressure Warning ECU and Receiver
      *3 ECM *4 Air Conditioning Amplifier Assembly
      *5 Airbag Sensor Assembly *6 Smart Key ECU Assembly (Certification ECU)
      *7 Power Steering ECU Assembly *8 Navigation Receiver Assembly
      *9 Radio and Display Receiver Assembly *10 Combination Meter Assembly
      *11 Power Management Control ECU *12 DLC3
      *13 Brake Booster with Master Cylinder Assembly (Skid Control ECU) *14 Steering Sensor
      *15 Main Body ECU (Multiplex Network Body ECU) *16 CAN Junction RH Connector
      *17 CAN Junction LH Connector - -
      A01I3V2E01
      Text in Illustration
      *a

      Component without harness connected

      (CAN Junction LH Connector)

      		 - -
      Wiring Color
      CAN Junction LH Connector Side Code Color (CANH Side) Color (CANL Side)
      CAN main bus line (bus line connecting CAN junction LH connector and CAN junction RH connector) I93 B W
      Combination meter assembly I94 R W
      Brake booster with master cylinder assembly (Skid control ECU) I110 Y W
      DLC3 I96 L W
      Power management control ECU I109 G W
      Steering sensor I97 V W
      Main body ECU (Multiplex network body ECU) I95 P W
      A01I3HUE01
      Text in Illustration
      *a

      Component without harness connected

      (CAN Junction RH Connector)

      		 - -
      Wiring Color
      CAN Junction RH Connector Side Code Color (CANH Side) Color (CANL Side)
      Clearance warning ECU assembly*1 I111 BE W
      Tire pressure warning ECU and receiver*2 I185 BE W
      ECM I104 P W
      Air conditioning amplifier assembly I102 V W
      Airbag sensor assembly I103 Y W
      Smart key ECU assembly (Certification ECU) I106 L W
      Power steering ECU assembly I100 G W

      • Navigation receiver assembly*3

      • Radio and display receiver assembly*4

      		 I107 R W
      CAN main bus line (bus line connecting CAN junction LH connector and CAN junction RH connector) I101 B W

      • *1: w/ Intuitive Parking Assist System

      • *2: for Tire Pressure Warning System with Tire Inflation Pressure Display Function

      • *3: for Navigation Receiver Type

      • *4: for Radio and Display Type

      Note

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

      Result
      Symptom Proceed to
      The resistance between terminals 6 (CANH) and 4 (CG), or the resistance between 14 (CANL) and 4 (CG) is still below 200 Ω when all the specified connectors are disconnected from the CAN junction connector. (There is a short to GND in the CAN main bus lines between the CAN junction LH connector and CAN junction RH connector.) A
      The resistance between terminals 6 (CANH) and 4 (CG), or the resistance between 14 (CANL) and 4 (CG) becomes normal (200 Ω or higher) when a connector is disconnected from the CAN junction connector. (There is a short to GND in one of the areas that relate to one or more of the disconnected bus lines.) B

    4. When there is a short to GND 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 GND). Check that the resistance shown on the tester is normal (200 Ω or higher) to confirm that there is a short to GND 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 wire harnesses, and to make future maintenance easier.

    5. When there is no short to GND 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 LH connector and CAN junction RH connector.


    B

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

    A

  3. CHECK FOR SHORT TO GND IN CAN BUS LINE (CAN J/C LH)


    1. A01I3NXE01
      Text in Illustration
      *a

      Rear view of wire harness connector

      (to CAN Junction LH Connector)
      *b to CAN Junction RH Connector

      Disconnect the I93 CAN junction LH connector.

      Note


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

      • Reconnect the connector to its original position.

    2. A01I5PBE49
      Text in Illustration
      *1 DLC3

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      I39-6 (CANH) - I39-4 (CG) Cable disconnected from negative (-) auxiliary battery terminal 200 Ω or higher
      I39-14 (CANL) - I39-4 (CG) Cable disconnected from negative (-) auxiliary battery terminal 200 Ω or higher

    NG

    REPLACE CAN JUNCTION LH CONNECTOR

    OK

  4. CHECK FOR SHORT TO GND IN CAN BUS LINE (CAN J/C LH - CAN J/C RH)


    1. Reconnect the I93 CAN junction LH connector.

    2. A01I2QJE01
      Text in Illustration
      *a

      Rear view of wire harness connector

      (to CAN Junction RH Connector)
      *b to CAN Junction LH Connector

      Disconnect the I101 CAN junction RH connector.

      Note


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

      • Reconnect the connector to its original position.

    3. A01I5PBE49
      Text in Illustration
      *1 DLC3

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      I39-6 (CANH) - I39-4 (CG) Cable disconnected from negative (-) auxiliary battery terminal 200 Ω or higher
      I39-14 (CANL) - I39-4 (CG) Cable disconnected from negative (-) auxiliary battery terminal 200 Ω or higher

    NG

    REPAIR OR REPLACE CAN MAIN BUS LINE (CAN J/C LH - CAN J/C RH)

    OK

    REPLACE CAN JUNCTION RH CONNECTOR

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


    1. Reconnect the connector of the bus line that is shorted to GND to the CAN junction connector (the connector that caused the bus line resistance to change to 200 Ω or higher when it was disconnected).

    2. 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 GND is connected Click here.

    3. A01I5PBE49
      Text in Illustration
      *1 DLC3

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      I39-6 (CANH) - I39-4 (CG) Cable disconnected from negative (-) auxiliary battery terminal 200 Ω or higher
      I39-14 (CANL) - I39-4 (CG) Cable disconnected from negative (-) auxiliary battery terminal 200 Ω or higher

      Tech Tips

      If the resistance changes to 200 Ω 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