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How To Proceed With Troubleshooting

WARNING: This page is about a different car, the 2011 Toyota Avalon. However, it is still accessible from the selected car via links, so may be relevant.
NOTE:
  • DTCs for the CAN communication system are as follows: U0073, U0100, U0123, U0124 and U0126.
  • Refer to the appropriate troubleshooting article of each system if DTCs regarding the CAN communication system are not output.

HINT: 

Use the Techstream.

  1. INSPECT BATTERY VOLTAGE 

    Standard voltage

    11 to 14 V

    HINT: 

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

    NEXT: Go to next step 

  2. CHECK AND CLEAR DTCs 

    HINT: 

    • 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 problems in the ECU, the sensor itself also cause these DTCs to be output.
    • If a CAN communication wire connector is disconnected with the ignition switch ON, the ECUs of the corresponding system and related systems record a DTC.

    NEXT: Go to next step 

  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. Refer to DIAGNOSIS SYSTEM .

      NEXT: Go to next step 

  4. CHECK DLC3 BRANCH WIRE AND CAN NO. 1 BUS CIRCUIT MAIN WIRE (CANH - CANL) 
    NOTE:
    • Turn the ignition switch off before measuring the resistances of the CAN main wire and the CAN branch wire.
    • After the ignition 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 ignition 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.

    HINT: 

    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.

    1. Turn the ignition switch off.
    2. Measure the resistance according to the value(s) in the table below.
      Fig 1: Identifying DLC3 Branch Wire And Can No. 1 Bus Circuit Main Wire
      GTY304361Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      TEXT IN ILLUSTRATION

      *1 DLC3

      Resistance

      Tester Connection Condition Specified value Proceed to
      D20-6 (CANH) - D20-14 (CANL) Ignition switch off 54 to 69 Ω A
      D20-6 (CANH) - D20-14 (CANL) Ignition switch off 70 Ω or higher B
      D20-6 (CANH) - D20-14 (CANL) Ignition switch off Below 54 Ω C

      B → GO TO CAN MAIN WIRE FOR DISCONNECTION. Refer to  CAN Main Bus Line for Disconnection  . 

      C → GO TO CHECK CAN BUS LINES FOR SHORT CIRCUIT. Refer to  Check CAN Bus Lines for Short Circuit  . 

      A: Go to next step 

  5. CHECK FOR SHORT TO GND IN CAN NO. 1 BUS (CANH, CANL - CG) 
    1. Turn the ignition switch off.
    2. Measure the resistance according to the value(s) in the table below.
      Fig 2: Identifying Short To GND In CAN No. 1 Bus
      GTY307635Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      TEXT IN ILLUSTRATION

      *1 DLC3

      Resistance

      Tester Connection Condition Specified value
      D20-6 (CANH) - D20-4 (CG) Ignition switch off 200 Ω or more
      D20-14 (CANL) - D20-4 (CG) Ignition switch off 200 Ω or more

      NG → GO TO CHECK CAN BUS LINE FOR SHORT TO GND. Refer to  Check CAN Bus Line for Short to GND  . 

      OK: Go to next step 

  6. CHECK FOR SHORT TO +B IN CAN NO. 1 BUS (CANH, CANL - BAT) 
    1. Disconnect the negative battery terminal.
    2. Measure the resistance according to the value(s) in the table below.
      Fig 3: Identifying Short To +B In CAN No. 1 Bus
      GTY304839Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      TEXT IN ILLUSTRATION

      *1 DLC3

      Resistance

      Tester Connection Condition Specified value
      D20-6 (CANH) - D20-16 (BAT) Cable disconnect from the negative (-) battery terminal 6 kΩ or more
      D20-14 (CANL) - D20-16 (BAT) Cable disconnect from the negative (-) battery terminal 6 kΩ or more

      NG → GO TO CHECK CAN BUS LINE FOR SHORT TO +B. Refer to  Check CAN Bus Line for Short to +B  . 

      OK: Go to next step 

  7. CHECK FOR INSTALLED SYSTEMS (ECUS & SENSORS) THAT USE CAN COMMUNICATION 
    1. Systems (ECUs, sensors) that adopt CAN communication vary depending on the vehicle and optional equipment. Check which systems (ECUs, sensors) are installed on the vehicle.

      NEXT: Go to next step 

  8. CHECK USING THE TECHSTREAM 
    1. Using the Techstream, display the "Communication Bus Check" screen. Refer to DIAGNOSIS SYSTEM 
    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 and 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.
      • Techstream 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". Refer to  PROBLEM SYMPTOMS TABLE  . 

      C → GO TO "OPEN IN ONE SIDE OF CAN BRANCH WIRE". Refer to  Open in One Side of CAN Sub Bus Line  . 

      A: Go to next step 

  9. DTC COMBINATION TABLE 
    1. Confirm trouble according to the combination of output DTCs regarding the CAN communication system. Refer to DIAGNOSIS SYSTEM .

      HINT: 

      • Sometimes CAN communication system DTCs are output, but all the ECUs and sensors connected to the CAN communication system are displayed on the Techstream. In this case, 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. The communication stop mode in the CAN bus can be determined by comparing the combination of DTCs that have been set. Refer to 4 the DTC combination table for the CAN bus.

      NEXT: Go to next step 

  10. CIRCUIT INSPECTION 

    NEXT: Go to next step 

  11. IDENTIFICATION OF PROBLEM 

    NEXT: Go to next step 

  12. REPAIR OR REPLACE 

    NEXT: Go to next step 

  13. CONFIRMATION TEST 

    NEXT → END 

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