Toyota Avalon (XX50) 2019-2022 Service & Repair Manual: Lost Communication with Front Seat Temperature Adjustment Switch LIN (B14B5)

Toyota Avalon (XX50) 2019-2022 Service & Repair Manual / Vehicle Interior / Seat / Seat Heater System(for Gasoline Model) / Lost Communication with Front Seat Temperature Adjustment Switch LIN (B14B5)

DESCRIPTION

The seat heater switch (radio and display receiver assembly) communicates with the air conditioning amplifier assembly via LIN communication.

If the LIN communication system is malfunctioning, the air conditioning amplifier assembly will not operate even if the seat heater switch (radio and display receiver assembly) is operated.

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

B14B5

Lost Communication with Front Seat Temperature Adjustment Switch LIN

Lost communication with the seat heater switch (radio and display receiver assembly)
  • Seat heater switch (radio and display receiver assembly)
  • Air conditioning amplifier assembly
  • Wire harness or connector
  • ECU-IG1 NO. 4 fuse

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

Inspect the fuses for circuits related to this system before performing the following procedure.

PROCEDURE

1.

CLEAR DTC

(a) Clear the DTCs.

Click here

Body Electrical > Air Conditioner > Clear DTCs
NEXT

2.

CHECK FOR DTC

(a) Check for DTCs.

Click here

Body Electrical > Air Conditioner > Trouble Codes

OK:

DTC B14B5 is not output.

OK

USE SIMULATION METHOD TO CHECK

NG

3.

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

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

*a

Front view of wire harness connector

(to Seat Heater Switch (Radio and Display Receiver Assembly))

(b) 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
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

4.

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

(a) Disconnect the G35 air conditioning amplifier assembly connector.

(b) 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
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

5.

INSPECT AIR CONDITIONING AMPLIFIER ASSEMBLY

(a) Connect the G35 air conditioning amplifier assembly connector.

(b) Turn the engine switch on (IG).

(c) Using an oscilloscope, check the waveform.

OK:

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)
NG

REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY

OK

6.

INSPECT SEAT HEATER SWITCH (RADIO AND DISPLAY RECEIVER ASSEMBLY)

*a

Component with harness connected

(Seat Heater Switch (Radio and Display Receiver Assembly))

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

(b) Turn the engine switch on (IG).

(c) 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)

OK:

Waveform is similar to that shown in the illustration.

OK

REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY

NG

REPLACE SEAT HEATER SWITCH (RADIO AND DISPLAY RECEIVER ASSEMBLY)

    Seat Heater System(for Gasoline Model)

    Front Right Seat Heat Sensor Circuit (B14C0)

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