AIR CONDITIONING SYSTEM, Diagnostic DTC:B149A

DTC Code DTC Name
B149A Communication Malfunction (Rear Bus Ic)

DESCRIPTION

The No. 2 air conditioning harness assembly connects the air conditioning amplifier assembly and the servo motors. The air conditioning amplifier assembly supplies power and sends operation instructions to each servo motor through the No. 2 air conditioning harness assembly. Each servo motor sends damper position information to the air conditioning amplifier assembly.

DTC No. Detection Item DTC Detection Condition Trouble Area Memory
B149A Communication Malfunction (Rear Bus Ic)

  • Diagnosis condition: None

  • Malfunction status: Error or open in communication line between air conditioning amplifier assembly and servo motor

  • No. 2 air conditioning harness assembly

  • No. 1 rear cooling unit damper servo sub-assembly

  • No. 1 blower damper servo sub-assembly

  • Air conditioning amplifier assembly

 Memorized

WIRING DIAGRAM

B004UFVE03

PROCEDURE


  1. PERFORM ACTIVE TEST USING GTS (SERVO PULSE)


    1. Connect the GTS to the DLC3.

    2. Turn the power switch on (IG).

    3. Turn the GTS on.

    4. Enter the following menus: Body Electrical / Air Conditioner / Active Test.

    5. Check the operation by referring to the table below.


      Body Electrical > Air Conditioner > Active Test
      Tester Display Measurement Item Control Range Restrict Condition
      A/O Servo Pulse(Rr D)

        for LHD:

      • No. 1 rear cooling unit damper servo sub-assembly (MODE LH) operation


        for RHD:

      • No. 1 rear cooling unit damper servo sub-assembly (MODE RH) operation

      Min.: 128

      Max.: 383

        for LHD:

      • Operates between 234 and 278 pulses


        for RHD:

      • Operates between 237 and 275 pulses
      A/O Servo Pulse(Rr P)

        for LHD:

      • No. 1 rear cooling unit damper servo sub-assembly (MODE RH) operation


        for RHD:

      • No. 1 rear cooling unit damper servo sub-assembly (MODE LH) operation

      Min.: 128

      Max.: 383

        for LHD:

      • Operates between 237 and 275 pulses


        for RHD:

      • Operates between 234 and 278 pulses

      Body Electrical > Air Conditioner > Active Test
      Tester Display
      A/O Servo Pulse(Rr D)
      OK
      Damper servo motor is operated.

      Body Electrical > Air Conditioner > Active Test
      Tester Display
      A/O Servo Pulse(Rr P)
      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

    B

    REPLACE NO. 2 AIR CONDITIONING HARNESS ASSEMBLY Click here

    C

    REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY Click here

    A

  2. CHECK AIR CONDITIONING AMPLIFIER ASSEMBLY (POWER SOURCE CIRCUIT)


    1. Disconnect the air conditioning amplifier assembly connector.

      B004UKKC01
      *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
      2 (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
      3 (RBBU) - Body ground Power switch off 11 to 14 V

    4. Using an oscilloscope, check the waveform.

      Item Content
      Tester Connection 22 (RBUS) - 2 (RBUG)
      Tool Setting 2 V/DIV., 20 μs/DIV.
      Condition Power switch on (IG)
      OK
      The waveform displays properly.
      Result
      Proceed to
      OK
      NG

    OK

    REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY Click here

    NG

    REPLACE NO. 2 AIR CONDITIONING HARNESS ASSEMBLY Click here