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Home >> Toyota >> 2021 >> Highlander LE, 4WD >> Repair and Diagnosis >> Heating, Ventilation & A/C (HVAC) >> HVAC Control Systems >> Heating / Air Conditioning System (Except HV, W/ Manual A/C) - Diagnostic Codes, Circuit Tests & Symptom Tests >> AIR CONDITIONING SYSTEM (for Gasoline Model with Manual Air Conditioning System) >> DTC B149A: Communication Malfunction (Rear Bus Ic) [12/2019 - 10/2022] >> Procedure

DTC B149A: Communication Malfunction (Rear Bus Ic) [12/2019 - 10/2022]: Procedure

  1. PERFORM ACTIVE TEST USING GTS (SERVO PULSE) 
    1. Perform the Active Test according to the display on the GTS.

      Body Electrical > Air Conditioner > Active Test 

      Tester Display Measurement Item Control Range Diagnostic Note
      Rear Air Mix Servo Targ Pulse Rear air mix damper servo sub-assembly pulse Min.: 128
      Max.: 383      		 Operates between 213 to 258 pulses
      A/O Servo Pulse (Rr D) Rear mode damper servo sub-assembly pulse Min.: 128
      Max.: 383      		 Operates between 200 to 276 pulses

      Body Electrical > Air Conditioner > Active Test 

      Tester Display
      Rear Air Mix Servo Targ Pulse

      Body Electrical > Air Conditioner > Active Test 

      Tester Display
      A/O Servo Pulse (Rr D)

      OK

      Damper servo motor is operated.

      Result

      Result  Proceed to
      All damper servo motors are not operated A
      Any damper servo motor is not operated B
      All damper servo motors are operated C

    Result: 

    B 

    REPLACE NO. 2 AIR CONDITIONING HARNESS ASSEMBLY. Refer to  DISASSEMBLY [12/2019 - ] 

    Result: 

    C 

    REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY. Refer to  REMOVAL [12/2019 - 10/2022] 

    Result: 

    A 

    See step  2

  2. CHECK AIR CONDITIONING AMPLIFIER ASSEMBLY 
    1. Disconnect the H64 air conditioning amplifier assembly connector.
      GTY846947Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Component without harness connected
      (Air Conditioning Amplifier Assembly)      		 - -
    2. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      H64-3 (RBUG) - Body ground Always Below 1 Ω
    3. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition
      H64-2 (RBBU) - H64-3 (RBUG) Ignition switch off 11 to 14 V
    4. Using an oscilloscope, check the waveform.
      Item Content
      Tester Connection H64-7 (RBUS) - H64-3 (RBUG)
      Tool Setting 2 V/DIV., 20 μs/DIV.
      Condition Ignition switch ON

      OK

      The waveform displays properly.

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY. Refer to  REMOVAL [12/2019 - 10/2022] 

    Result: 

    OK 

    See step  3

  3. CHECK HARNESS AND CONNECTOR (AIR CONDITIONING AMPLIFIER ASSEMBLY - NO. 2 AIR CONDITIONING HARNESS ASSEMBLY) 
    1. Connect the H64 air conditioning amplifier assembly connector.
      GTY868048Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Front view of wire harness connector
      (to No. 2 Air Conditioning Harness Assembly)
    2. Disconnect the M15 No. 2 air conditioning harness assembly connector.
    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      M15-2 (RBUG) - Body ground Always Below 1 Ω
    4. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition
      M15-4 (RBBU) - M15-2 (RBUG) Ignition switch off 11 to 14 V
    5. Using an oscilloscope, check the waveform.
      Item Content
      Tester Connection M15-3 (RBUS) - M15-2 (RBUG)
      Tool Setting 2 V/DIV., 20 μs/DIV.
      Condition Ignition switch ON

      OK

      The waveform displays properly.

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPLACE NO. 2 AIR CONDITIONING HARNESS ASSEMBLY. Refer to  DISASSEMBLY [12/2019 - ] 

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR (AIR CONDITIONING AMPLIFIER ASSEMBLY - NO. 2 AIR CONDITIONING HARNESS ASSEMBLY) 

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