DTC B149A: Communication Malfunction (Rear Bus Ic) [12/2019 - 11/2023]: Procedure

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]  , or refer to  REMOVAL [10/2022 - 11/2023] 

Result: 

A 

See step  2

1. Disconnect the H64 air conditioning amplifier assembly connector.

   Courtesy 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]  , or refer to  REMOVAL [10/2022 - 11/2023] 

Result: 

OK 

See step  3

1. Connect the H64 air conditioning amplifier assembly connector.

   Courtesy 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)