DTC B142A-88: Servo Motor LIN Communication Bus off [11/2021 - ]: Procedure

1. Disconnect the z21 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
   z21-2 (BUS G) - 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
   z21-4 (B BUS) - z21-2 (BUS G)	Ignition switch off	11 to 14 V

4. Using an oscilloscope, check the waveform.

   Item	Content
   Tester Connection	z21-3 (BUS) - z21-2 (BUS G)
   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 [11/2021 - ] 

Result: 

OK 

See step  2

1. Disconnect the z21 air conditioning amplifier assembly connector.
2. Disconnect the A No. 1 air conditioning radiator damper servo sub-assembly connector.
3. Measure the resistance according to the value(s) in the table below.

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   *a

   Front view of wire harness connector (to No. 1 Air Conditioning Radiator Damper Servo Sub-assembly)

   *b

   Front view of wire harness connector (to Air Conditioning Amplifier Assembly)

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   z21-2 (BUS G) - A-6 (BUS G)	Always	Below 1 Ω
   z21-3 (BUS) - A-7 (BUS)	Always	Below 1 Ω
   z21-4 (B BUS) - A-8 (B BUS)	Always	Below 1 Ω

   Result

   Proceed to
   OK
   NG

Result: 

OK 

REPLACE NO. 1 AIR CONDITIONING RADIATOR DAMPER SERVO SUB-ASSEMBLY. Refer to  DISASSEMBLY [11/2021 - ] 

Result: 

NG 

REPLACE AIR CONDITIONING HARNESS ASSEMBLY. Refer to  DISASSEMBLY [11/2021 - ]