CAN COMMUNICATION SYSTEM HOW TO PROCEED WITH TROUBLESHOOTING

Note


  • DTCs for the CAN communication system are as follows:

    U0073, U0100, U0101, U0122, U0123, U0124, U0126, U0129, U0140, U0146, U0151 and U1101.

  • Refer to troubleshooting of each system if DTCs regarding the CAN communication system are not output.

Tech Tips

*: Use the intelligent tester.


  1. INSPECT BATTERY VOLTAGE

    Standard voltage
    11 to 14 V

    Tech Tips

    If the voltage is below 11 V, recharge or replace the battery before proceeding to the next step.


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  2. CHECK AND CLEAR DTCS*

    Tech Tips


    • CAN communication DTCs are output when there is an open or short in any of the communication wires. Any problems with the power source of a corresponding ECU or sensor, or in the ECU or sensor itself cause these DTCs to be output.

    • If a CAN communication wire connector is disconnected with the engine switch on (IG), the ECUs of the corresponding system and related systems store a DTC.

    • Record or print DTCs.


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  3. CHECK INSTALLED SYSTEMS (ECU AND SENSOR) THAT USE CAN COMMUNICATION


    1. Based on the vehicle equipment and specifications, confirm the systems that use CAN communication Click here.


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  4. CHECK DLC3 BRANCH WIRE AND CAN NO. 1 BUS CIRCUIT MAIN WIRE (CANH - CANL)

    Note


    • Turn the engine switch off before measuring the resistances of the CAN main wire and the CAN branch wire.

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

    • 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 the doors need to be opened in order to check the connectors, open the doors and leave them open.

    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.


    1. Turn the engine switch off.

    2. A0161HNE24

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

      Standard Resistance
      Tester Connection Switch Condition Specified Value Proceed to
      J21-6 (CANH) - J21-14 (CANL) Engine switch off 54 to 69 Ω A
      J21-6 (CANH) - J21-14 (CANL) Engine switch off 70 Ω or higher B
      J21-6 (CANH) - J21-14 (CANL) Engine switch off Below 54 Ω C

      B

      GO TO "OPEN IN CAN MAIN WIRE" Click here for LHD, Click here for RHD
      C

      GO TO "SHORT IN CAN BUS LINES" Click here for LHD, Click here for RHD
      A

  5. CHECK FOR SHORT TO GND IN CAN NO. 1 BUS (CANH, CANL - CG)


    1. Turn the engine switch off.

    2. A0161HNE26

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

      Standard Resistance
      Tester Connection Switch Condition Specified Value
      J21-6 (CANH) - J21-4 (CG) Engine switch off 200 Ω or higher
      J21-14 (CANL) - J21-4 (CG) Engine switch off 200 Ω or higher

      NG

      GO TO "SHORT TO GND IN CAN BUS LINE" Click here for LHD, Click here for RHD
      OK

  6. CHECK FOR SHORT TO +B IN CAN NO. 1 BUS (CANH, CANL - BAT)


    1. Disconnect the negative battery terminal.

    2. 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

      GO TO "SHORT TO +B IN CAN BUS LINE" Click here for LHD, Click here for RHD
      OK

  7. CHECK FOR INSTALLED SYSTEMS (ECUS & SENSORS) THAT ADOPT CAN COMMUNICATION


    1. Check which of the following is adopted: dynamic radar cruise control and LEXUS navigation system.


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  8. CHECK INTELLIGENT TESTER


    1. Using the intelligent tester, select "Communication Bus Check".

    2. Observe the screen for approximately 1 minute to check the ECUs and sensors displayed on the screen.

      Result
      Result Proceed to

      All ECUs and sensors connected to the CAN communication system are displayed on the screen.

      (CAN bus circuit is currently normal)

      		 A

      One of the ECUs or sensors connected to the CAN communication system is not displayed on the screen.

      (Open in ECU or sensor branch wires, or communication interrupted)

      		 B

      Some ECUs and sensors repeatedly appear and disappear from the screen during this check.

      (Open in one side of ECU or sensor branch wires)

      		 C

      Note


      • The systems (ECUs, sensors) that adopt CAN communication vary depending on the vehicle and option settings. Check which systems (ECUs, sensors) are installed on the vehicle.

      • Non-installed ECUs or sensors are not displayed. Do not mistake them for being in communication stop mode.

      • The intelligent tester display is affected by signals output from other ECUs which have an open circuit in either of their CAN branch wires.


      B

      GO TO "COMMUNICATION STOP MODE TABLE" Click here

      C

      GO TO "OPEN IN ONE SIDE OF CAN BRANCH LINE" Click here

      A

  9. DTC COMBINATION TABLE


    1. Confirm trouble according to the combination of output DTCs regarding the CAN communication system Click here.

      Tech Tips


      • Sometimes CAN communication system DTCs are output, but all the ECUs and sensors connected to the CAN communication system are displayed on the intelligent tester. In this case, previous or history DTCs may indicate the cause of the problem.

      • ECUs related to a problem in the CAN bus will store DTCs to indicate communication malfunctions. Communication stop mode in the CAN bus can be determined by comparing the combination of DTCs that have been set. Refer to the DTC combination table for the CAN bus.


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  10. CIRCUIT INSPECTION


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  11. IDENTIFICATION OF PROBLEM


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  12. REPAIR OR REPLACE


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  13. CONFIRMATION TEST


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    END