DTC B1279: Lost Communication with Humidity/Rain Sensor LIN [10/2019 - 10/2020]: Procedure

1. Disconnect the F41 main body ECU (multiplex network body ECU) connector.
2. Disconnect the S2 air conditioning thermistor assembly*1 or rain sensor*2 connector.
3. Measure the resistance according to the value(s) in the table below.
   1. *1: w/o Rain Sensor
   2. *2: w/ Rain Sensor

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   S2-3 (MPX) - F41-3 (LIN3)	Always	Below 1 Ω
   S2-3 (MPX) or F41-3 (LIN3) - Body ground	Always	10 kΩ or higher

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPAIR OR REPLACE HARNESS OR CONNECTOR 

Result: 

OK 

See step  2

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

1. Using an oscilloscope, check the waveform.

   OK

   Tester Connection	Switch Condition	Specified Condition
   F41-3 (LIN3) -Body ground	Power switch on (IG)	Pulse generation

   Result

   Result	Proceed to
   OK (w/o Rain Sensor)	A
   OK (w/ Rain Sensor)	B
   NG	C

Result: 

A 

REPLACE AIR CONDITIONING THERMISTOR ASSEMBLY. Refer to  REMOVAL [10/2018 - 10/2020] 

Result: 

B 

REPLACE RAIN SENSOR. Refer to  REMOVAL [10/2018 - ] 

Result: 

C 

REPLACE MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU). Refer to  REMOVAL [10/2018 - 07/2022]