DTC B14B2-87: Lost Communication with Front Panel LIN Missing Message [09/2022 - ]: Procedure

1. Disconnect the I37 air conditioning control assembly connector.
2. Measure the voltage according to the value(s) in the table below.

   Standard Voltage

   Tester Connection	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. Disconnect the I37 air conditioning control assembly connector.
2. 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 I37 air conditioning control assembly connector.
2. Disconnect the I49 air conditioning amplifier assembly connector.
3. 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. Disconnect the I37 air conditioning control assembly connector.
2. Connect the I49 air conditioning amplifier assembly connector.
3. Using an oscilloscope, check the waveform.

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

   OK

   The waveform displays properly.

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY 

Refer to REMOVAL [09/2022 - 11/2022] , or refer to REMOVAL [11/2022 - ]

Result: 

OK 

See step  5

1. Connect the I37 air conditioning control assembly connector.
2. Using an oscilloscope, check the waveform.

   Item	Content
   Tester Connection	I37-7 (LIN1) - Body ground
   Tool Setting	2 V/DIV., 20 μs/DIV.
   Condition	Ignition switch ON

   OK

   The waveform displays properly.

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   Result

   Proceed to
   OK
   NG

Result: 

OK 

REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY 

Refer to REMOVAL [09/2022 - 11/2022] , or refer to REMOVAL [11/2022 - ]

Result: 

NG 

REPLACE AIR CONDITIONING CONTROL ASSEMBLY 

Refer to REMOVAL [06/2018 - 09/2024] , or refer to REMOVAL [09/2024 - ]