DTC B14B5: Lost Communication with Front Seat Temperature Adjustment Switch LIN [04/2018 - ]: Procedure

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CLEAR DTC

Clear the DTCs.

Refer to DTC CHECK / CLEAR [04/2018 - ]

Body Electrical > Air Conditioner > Clear DTCs

Result

Proceed to
NEXT

Result:

See step 2

CHECK FOR DTC

Check for DTCs.

Refer to DTC CHECK / CLEAR [04/2018 - ]

Body Electrical > Air Conditioner > Trouble Codes

DTC B14B5 is not output.

Result

Proceed to
OK
NG

Result:

USE SIMULATION METHOD TO CHECK. Refer to HOW TO PROCEED WITH TROUBLESHOOTING [04/2018 - ]

Result:

See step 3

CHECK HARNESS AND CONNECTOR (IG POWER SUPPLY - SEAT HEATER SWITCH (RADIO AND DISPLAY RECEIVER ASSEMBLY) - BODY GROUND)

Disconnect the G20 seat heater switch (radio and display receiver assembly) connector.

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

*a	Front view of wire harness connector (to Seat Heater Switch (Radio and Display Receiver Assembly))

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

Standard Voltage

Tester Connection	Condition	Specified Condition
G20-2 (IG+) - Body ground	Engine switch on (IG)	11 to 14 V
G20-2 (IG+) - Body ground	Engine switch off	Below 1 V

Standard Resistance

Tester Connection	Condition	Specified Condition
G20-6 (GND) - Body ground	Always	Below 1 Ω

Result

Proceed to
OK
NG

Result:

REPAIR OR REPLACE HARNESS OR CONNECTOR

Result:

See step 4

CHECK HARNESS AND CONNECTOR (AIR CONDITIONING AMPLIFIER ASSEMBLY - SEAT HEATER SWITCH (RADIO AND DISPLAY RECEIVER ASSEMBLY))

Disconnect the G35 air conditioning amplifier assembly connector.

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

Standard Resistance

Tester Connection	Condition	Specified Condition
G35-14 (LIN1) - G20-8 (LIN1)	Always	Below 1 Ω
G35-14 (LIN1) or G20-8 (LIN1) - Body ground	Always	10 kΩ or higher

Result

Proceed to
OK
NG

Result:

REPAIR OR REPLACE HARNESS OR CONNECTOR

Result:

See step 5

INSPECT AIR CONDITIONING AMPLIFIER ASSEMBLY

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

Connect the G35 air conditioning amplifier assembly connector.
Turn the engine switch on (IG).

Using an oscilloscope, check the waveform.

Waveform is similar to that shown in the illustration.

Item	Content
Terminal No.	G35-14 (LIN1) - Body ground
Tool Setting	2 V/DIV., 20 ms./DIV.
Condition	Engine switch on (IG)

Result

Proceed to
OK
NG

Result:

REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY. Refer to REMOVAL [04/2018 - 08/2020] , or refer to REMOVAL [08/2020 - ]

Result:

See step 6

INSPECT SEAT HEATER SWITCH (RADIO AND DISPLAY RECEIVER ASSEMBLY)

*a	Component with harness connected (Seat Heater Switch (Radio and Display Receiver Assembly))

Connect the G20 seat heater switch (radio and display receiver assembly) connector.
Turn the engine switch on (IG).

Using an oscilloscope, check the waveform.

Item	Content
Terminal No.	G20-8 (LIN1) - Body ground
Tool Setting	2 V/DIV., 20 ms./DIV.
Condition	Engine switch on (IG)

Waveform is similar to that shown in the illustration.

Result

Proceed to
OK
NG

Result:

REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY. Refer to REMOVAL [04/2018 - 08/2020] , or refer to REMOVAL [08/2020 - ]

Result:

REPLACE SEAT HEATER SWITCH (RADIO AND DISPLAY RECEIVER ASSEMBLY). Refer to REMOVAL [04/2018 - ]