DTC B14B2-87: Lost Communication with Front Panel LIN Missing Message [11/2022 - ]: Procedure

1. Disconnect the air conditioning control assembly connector.

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   *a	Front view of wire harness connector (to Air Conditioning Control Assembly)

2. Measure the voltage according to the value(s) in the table below.

   Standard Voltage

   Tester Connection	Switch Condition	Specified Condition
   I37-9 (IG+) - Body ground	Ignition switch ON	11 to 14 V

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPAIR OR REPLACE HARNESS OR CONNECTOR 

Result: 

OK 

See step  2

1. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   I37-13 (GND) - Body ground	Always	Below 1 Ω

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPAIR OR REPLACE HARNESS OR CONNECTOR 

Result: 

OK 

See step  3

1. Disconnect the I49 air conditioning amplifier assembly connector.
2. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   I37-7 (LIN1) - I49-7 (LIN1)	Always	Below 1 Ω
   I37-7 (LIN1) or I49-7 (LIN1) - Other terminals and body ground	Always	10 kΩ or higher

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPAIR OR REPLACE HARNESS OR CONNECTOR 

Result: 

OK 

See step  4

1. Using an oscilloscope, check the waveform.

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   *a

   Component with harness connected (Air Conditioning Amplifier Assembly)

   -

   -

   Tester Connection	Tool Setting	Switch Condition
   I49-7 (LIN1) - Body ground	2 V/DIV., 20 ms./DIV.	Ignition switch ON

   OK

   Waveform is similar to that shown in the illustration.

   Result

   Proceed to
   OK
   NG

Result: 

OK 

REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY 

Refer to REMOVAL [11/2022 - ]

Result: 

NG 

REPLACE AIR CONDITIONING CONTROL ASSEMBLY 

Refer to REMOVAL [09/2021 - ]