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

DESCRIPTION

A short to B+ is suspected in the CAN bus line when the resistance between terminals 6 (CANH) and 16 (BAT), or terminals 14 (CANL) and 16 (BAT) of the DLC3 is below 6 kΩ.

Symptom Trouble Area
The resistance between terminals 6 (CANH) and 16 (BAT), or terminals 14 (CANL) and 16 (BAT) of the DLC3 is below 6 kΩ.

Short to B+ in CAN bus line


  • Skid control ECU (Brake actuator assembly)

  • Steering angle sensor

  • Yaw rate sensor

  • ECM

  • Gateway ECU

  • Distance control ECU

  • Seat belt control ECU

  • Parking assist ECU

  • Power steering ECU

  • Center airbag sensor

  • Navigation ECU (Display and navigation module display)

WIRING DIAGRAM

A0162VLE07
A01610UE12

INSPECTION PROCEDURE

Note


  • Turn the engine switch off before measuring the resistance of CAN bus main wires and CAN bus branch wires.

  • After the engine switch is turned off, check that the key reminder warning system and light reminder warning system are not operating.

  • Before measuring the resistance, leave the vehicle as is for at least 1 minute and do not operate the engine switch, any other switches, or the doors. If any doors need to be opened in order to check connectors, open the doors and leave them open.

Tech Tips

Operating the engine switch, any switches, or any doors triggers related ECU and sensor communication with the CAN. This communication will cause the resistance value to change.

PROCEDURE


  1. CHECK FOR SHORT TO B+ IN CAN BUS WIRE


    1. Turn the engine switch off.

    2. A0161BKE24

      Disconnect the DLC3 branch line connector (J8) from the CAN LH junction connector B side (w/o earth terminal).

      Note


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

      • Reconnect the connector to its original position.

    3. A0161HNE25

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

      Standard Resistance
      Tester Connection Condition Specified Value
      J21-6 (CANH) - J21-16 (BAT) Cable from negative battery terminal disconnected 6 kΩ or higher
      J21-14 (CANL) - J21-16 (BAT) Cable from negative battery terminal disconnected 6 kΩ or higher

    NG
    OK
  2. RECONNECT CONNECTOR


    1. Reconnect the DLC3 branch line connector (J8) to the CAN LH junction connector B side (w/o earth terminal).


    NEXT
  3. CHECK FOR SHORT TO B+ IN CAN BUS WIRE


    1. A0161HNE25

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

    2. 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.

      A0162HKE02
      A01622BE03
      Wiring Color
      CAN LH Junction Connector 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 J3 V W
      Center airbag sensor J4 R W
      Wiring Color
      CAN LH Junction Connector B Side (w/o Earth Terminal) Code Color (CANH Side) Color (CANL Side)
      Yaw rate sensor J5 P W
      CAN main bus line (bus line connecting CAN LH junction connector and CAN RH junction connector) J7 B W
      DLC3 J8 G W
      Distance control ECU J9 GR W
      Skid control ECU (Brake actuator assembly) J128 R W
      A015ZHNE02
      Wiring Color
      CAN RH Junction Connector A Side (w/ Earth Terminal) Code Color (CANH Side) Color (CANL Side)
      CAN main bus line (bus line connecting CAN RH junction connector and CAN LH junction connector) J81 B W
      Power steering ECU J82 P W
      Parking assist ECU J94 L W
      Wiring Color
      CAN RH Junction Connector B Side (w/o Earth Terminal) Code Color (CANH Side) Color (CANL Side)
      Gateway ECU J84 B W
      Navigation ECU (Display and navigation module display) J116 SB W

      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 LH junction connector and CAN RH junction connector.) 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 related to one or more of the disconnected bus lines.) B
    3. 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 only one bus line.

        Tech Tips


        • The connectors connected to the CAN junction connector 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 junction connector 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
    A
  4. RECONNECT CONNECTOR


    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).


    NEXT
  5. CHECK FOR SHORT TO B+ IN CAN BUS WIRE


    1. A0161HNE25

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

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

      Standard Resistance
      Tester Connection Condition Specified Value
      J21-6 (CANH) - J21-16 (BAT) Cable from negative battery terminal disconnected 6 kΩ or higher
      J21-14 (CANL) - J21-16 (BAT) Cable from negative battery terminal disconnected 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
    OK