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DTC B1279: Lost Communication with Humidity/Rain Sensor LIN [12/2019 - 10/2021]: Procedure

WARNING: This page is about a different variant/trim than selected.
  1. CHECK FOR DTC 
    1. Check for DTCs.

      Body Electrical > Main Body > Trouble Codes 

      Result

      Result Proceed to
      DTC B1279 is output (w/o Auto Wiper System) A
      DTC B1279 is output (w/ Auto Wiper System) B
      DTC B1279 and B1373 are output C

    Result: 

    B 

    See step  5

    Result: 

    C 

    GO TO B1373. Refer to  DTC B1373: Lost Communication with Wiper System LIN BUS [12/2019 - 11/2023] 

    Result: 

    A 

    See step  2

  2. CHECK HARNESS AND CONNECTOR (WINDSHIELD HUMIDITY SENSOR (AIR CONDITIONING THERMISTOR ASSEMBLY) - MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU)) 
    1. Disconnect the H42 main body ECU (multiplex network body ECU) connector.
    2. Disconnect the R4 windshield humidity sensor (air conditioning thermistor assembly) connector.
    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      R4-3 (MPX) - H42-3 (LIN3) Always Below 1 Ω
      R4-3 (MPX) or H42-3 (LIN3) - Body ground Always 10 kΩ or higher

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  3

  3. INSPECT MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU) 
    1. Disconnect the H42 main body ECU (multiplex network body ECU) connector.
    2. Check for voltage and pulses according to the value(s) in the table below.
      GTY909919Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Component without harness connected
      (Main Body ECU (Multiplex Network Body ECU))      		 - -

      Standard Voltage

      Tester Connection Condition Specified Condition
      H42-3 (LIN3) - Body ground Ignition switch off Below 1 V
      Ignition switch ON Pulse generation

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPLACE MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU). Refer to  REMOVAL [12/2019 - 10/2022] 

    Result: 

    OK 

    See step  4

  4. CHECK HARNESS AND CONNECTOR (POWER SOURCE - WINDSHIELD HUMIDITY SENSOR (AIR CONDITIONING THERMISTOR ASSEMBLY)) 
    1. Disconnect the R4 windshield humidity sensor (air conditioning thermistor assembly) connector.
    2. Measure the voltage and resistance according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition
      R4-4 (SIG) - Body ground Ignition switch ON 11 to 14 V
      Ignition switch off Below 1 V

      Standard Resistance

      Tester Connection Condition Specified Condition
      R4-2 (ES) - Body ground Always Below 1 Ω

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPLACE WINDSHIELD HUMIDITY SENSOR (AIR CONDITIONING THERMISTOR ASSEMBLY). Refer to  REMOVAL [12/2019 - 10/2021] 

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

  5. CHECK HARNESS AND CONNECTOR (WINDSHIELD HUMIDITY SENSOR (RAIN SENSOR) - MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU)) 
    1. Disconnect the H42 main body ECU (multiplex network body ECU) connector.
    2. Disconnect the R4 windshield humidity sensor (rain sensor) connector.
    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      R4-3 (MPX) - H42-3 (LIN3) Always Below 1 Ω
      R4-3 (MPX) or H42-3 (LIN3) - Body ground Always 10 kΩ or higher

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  6

  6. INSPECT MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU) 
    1. Disconnect the H42 main body ECU (multiplex network body ECU) connector.
    2. Check for voltage and pulses according to the value(s) in the table below.
      GTY909919Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Component without harness connected
      (Main Body ECU (Multiplex Network Body ECU))      		 - -

      Standard Voltage

      Tester Connection Condition Specified Condition
      H42-3 (LIN3) - Body ground Ignition switch off Below 1 V
      Ignition switch ON Pulse generation

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPLACE MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU). Refer to  REMOVAL [12/2019 - 10/2022] 

    Result: 

    OK 

    See step  7

  7. CHECK HARNESS AND CONNECTOR (POWER SOURCE - WINDSHIELD HUMIDITY SENSOR (RAIN SENSOR)) 
    1. Disconnect the R4 windshield humidity sensor (rain sensor) connector.
    2. Measure the voltage and resistance according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition
      R4-4 (SIG) - Body ground Ignition switch ON 11 to 14 V
      Ignition switch off Below 1 V

      Standard Resistance

      Tester Connection Condition Specified Condition
      R4-2 (ES) - Body ground Always Below 1 Ω

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPLACE WINDSHIELD HUMIDITY SENSOR (RAIN SENSOR). Refer to  REMOVAL [12/2019 - ] 

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

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