Toyota Avalon (XX50): Seat Heater System(for Hv 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.

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

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

PROCEDURE

(a) Clear the DTCs.

Click here

NEXT

(a) Check for DTCs.

Click here

OK:

DTC B14B5 is not output.

OK

USE SIMULATION METHOD TO CHECK

NG

(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:

Standard Resistance:

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

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

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

Standard Resistance:

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

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

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

(c) Using an oscilloscope, check the waveform.

OK:

Waveform is similar to that shown in the illustration.

NG

REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY

OK

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

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

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

(c) Using an oscilloscope, check the waveform.

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)

Front Right Seat Heat Sensor Circuit (B14C0)

DESCRIPTION

Output to the front seat cushion heater temperature sensor stops if one of the following occurs: 1) the temperature sensor is open or shorted; or 2) the temperature sensor is damaged and its output value does not change.

WIRING DIAGRAM

PROCEDURE

(a) Clear the DTCs.

Click here

NEXT

(a) Check for DTCs.

Click here

OK:

DTC B14C0 is not output.

OK

USE SIMULATION METHOD TO CHECK

NG

(a) Disconnect the R6 front seat cushion heater assembly RH connector.

(b) Measure the resistance according to the value(s) in the table below. Standard Resistance: Tester Connection Condition Specified Condition R6-4 (THR) - R6-5 (PR) Seat heater temperature 25°C (77°F) 9.5 to 10.5 kΩ

*a Component without harness connected (Front Seat Cushion Heater Assembly RH)

NG

REPLACE FRONT SEAT CUSHION HEATER ASSEMBLY RH

OK

(a) Disconnect the G37 air conditioning amplifier assembly connector.

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

Standard Resistance:

OK

REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

Front Left Seat Heat Sensor Circuit (B14C1)

DESCRIPTION

Output to the front seat cushion heater temperature sensor stops if one of the following occurs: 1) the temperature sensor is open or shorted; or 2) the temperature sensor is damaged and its output value does not change.

WIRING DIAGRAM

PROCEDURE

(a) Clear the DTCs.

Click here

NEXT

(a) Check for DTCs.

Click here

OK:

DTC B14C1 is not output.

OK

USE SIMULATION METHOD TO CHECK

NG

(a) Disconnect the R26 front seat cushion heater assembly LH connector.

(b) Measure the resistance according to the value(s) in the table below. Standard Resistance: Tester Connection Condition Specified Condition R26-4 (THL) - R26-5 (PL) Seat heater temperature 25°C (77°F) 9.5 to 10.5 kΩ

*a Component without harness connected (Front Seat Cushion Heater Assembly LH)

NG

REPLACE FRONT SEAT CUSHION HEATER ASSEMBLY LH

OK

(a) Disconnect the G36 and G37 air conditioning amplifier assembly connectors.

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

Standard Resistance:

OK

REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

Data List / Active Test

DATA LIST / ACTIVE TEST

DATA LIST

NOTICE:

In the following table, the values listed under "Normal Condition" are reference values. Do not depend solely on these reference values when deciding whether a part is faulty or not.

HINT:

Using the Techstream to read the Data List allows the values or states of switches, sensors, actuators and other items to be read without removing any parts. This non-intrusive inspection can be very useful because intermittent conditions or signals may be discovered before parts or wiring is disturbed. Reading the Data List information early in troubleshooting is one way to save diagnostic time.

(a) Connect the Techstream to the DLC3.

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

(c) Turn the Techstream on.

(d) Enter the following menus: Body Electrical / Air Conditioner / Data List.

(e) Read the Data List according to the display on the Techstream.

ACTIVE TEST

HINT:

Using the Techstream to perform Active Tests allows relays, VSVs, actuators and other items to be operated without removing any parts. This non-intrusive functional inspection can be very useful because intermittent operation may be discovered before parts or wiring is disturbed. Performing Active Tests early in troubleshooting is one way to save diagnostic time. Data List information can be displayed while performing Active Tests.

(a) Connect the Techstream to the DLC3.

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

(c) Turn the Techstream on.

(d) Enter the following menus: Body Electrical / Air Conditioner / Active Test.

(e) Perform the Active Test according to the display on the Techstream.

Diagnosis System

DIAGNOSIS SYSTEM

DESCRIPTION

(a) Seat heater system data and Diagnostic Trouble Codes (DTCs) can be read through the Data Link Connector 3 (DLC3) of the vehicle. When the system seems to be malfunctioning, use the Techstream to check for malfunctions and perform repairs.

CHECK DLC3

(a) Check the DLC3.

Click here

INSPECT AUXILIARY BATTERY VOLTAGE

(a) Check the auxiliary battery voltage with the power switch.

Standard Voltage:

11 to 14 V

If the voltage is below 11 V, recharge or replace the auxiliary battery.

Diagnostic Trouble Code Chart

DIAGNOSTIC TROUBLE CODE CHART

Dtc Check / Clear

DTC CHECK / CLEAR

CHECK DTC

(a) Connect the Techstream to the DLC3.

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

(c) Turn the Techstream on.

(d) Enter the following menus: Body Electrical / Air Conditioner / Trouble Codes.

(e) Check for DTCs.

CLEAR DTC

(a) Connect the Techstream to the DLC3.

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

(c) Turn the Techstream on.

(d) Enter the following menus: Body Electrical / Air Conditioner / Trouble Codes.

(e) Clear the DTCs.

How To Proceed With Troubleshooting

CAUTION / NOTICE / HINT

HINT:

• Use the following procedure to troubleshoot the seat heater system.
• *: Use the Techstream.

PROCEDURE

NEXT

(a) Interview the customer to confirm the problem.

Click here

NEXT

(a) Measure the auxiliary battery voltage with the power switch off.

Standard Voltage:

11 to 14 V

If the voltage is below 11 V, recharge or replace the auxiliary battery before proceeding to the next step.

(b) Check the fuses and relays.

(c) Check the connector connections and terminals to make sure that there are no abnormalities such as loose connections, deformation, etc.

NEXT

(a) Clear the DTCs.

(b) Check for DTCs.

B

GO TO AIR CONDITIONING SYSTEM

C

GO TO DIAGNOSTIC TROUBLE CODE CHART

A

(a) Refer to Problem Symptoms Table.

Click here

B

GO TO STEP 7

A

(a) Operation Check

Click here

(b) Terminals of ECU

Click here

(c) Data List / Active Test

Click here

(d) Inspection

NEXT

NEXT

NEXT

END

Operation Check

OPERATION CHECK

CHECK FRONT SEAT HEATER

(a) Turn the power switch on (IG).

(b) Turn the seat heater switch (radio and display receiver assembly) on and check that the indicator illuminates and the surface of the front seat warms up.

(c) Check that the front seat surface temperature changes according to the operation of the seat heater switch (radio and display receiver assembly) as follows: HI → MID → LO.

CHECK REAR SEAT HEATER (w/ Rear Seat Heater)

(a) Turn the power switch on (IG).

(b) Turn the seat heater switch on and check that the indicator illuminates and the surface of the rear seat warms up.

CHECK THERMOSTAT OF SEAT HEATER ASSEMBLY (REAR SEAT CUSHION HEATER LH) (w/ Rear Seat Heater)

(a) Remove the seat heater assembly (rear seat cushion heater LH).

Click here

(b) Remove the seat heater assembly (rear seatback heater LH).

Click here

(c) Connect the B seat heater assembly (rear seatback heater LH) connector and A seat heater assembly (rear seat cushion heater LH) connector.

(d) Apply auxiliary battery voltage and check the operation of the rear seat heater as shown in the table below.

NOTICE:

To prevent the rear seat heater from overheating, be sure to disconnect the auxiliary battery from the rear seat heater immediately after this inspection is completed.

OK:

CHECK THERMOSTAT OF SEAT HEATER ASSEMBLY (REAR SEAT CUSHION HEATER RH) (w/ Rear Seat Heater)

(a) Remove the seat heater assembly (rear seat cushion heater RH).

Click here

(b) Remove the seat heater assembly (rear seatback heater RH).

Click here

(c) Connect the C seat heater assembly (rear seat cushion heater RH) connector and D seat heater assembly (rear seatback heater RH) connector.

(d) Apply auxiliary battery voltage and check the operation of the rear seat heater as shown in the table below.

NOTICE:

To prevent the rear seat heater from overheating, be sure to disconnect the auxiliary battery from the rear seat heater immediately after this inspection is completed.

OK:

Parts Location

PARTS LOCATION

ILLUSTRATION

ILLUSTRATION

ILLUSTRATION

ILLUSTRATION

Precaution

PRECAUTION

PRECAUTION FOR DISCONNECTING CABLE FROM NEGATIVE AUXILIARY BATTERY TERMINAL

NOTICE:

When disconnecting the cable from the negative (-) auxiliary battery terminal, initialize the following systems after the cable is reconnected.

Problem Symptoms Table

PROBLEM SYMPTOMS TABLE

NOTICE:

• If the auxiliary battery voltage becomes low, auxiliary battery load control will operate in order to ensure sufficient power is supplied to the power steering system. In this case, the seat heater system (for HV model) may not operate.

HINT:

• Use the table below to help determine the cause of problem symptoms. If multiple suspected areas are listed, the potential causes of the symptoms are listed in order of probability in the "Suspected Area" column of the table. Check each symptom by checking the suspected areas in the order they are listed. Replace parts as necessary.
• Inspect the fuses and relays related to this system before inspecting the suspected areas below.

Seat Heater for Front Left Seat does not Operate

DESCRIPTION

When the seat heater switch of the seat heater switch (radio and display receiver assembly) is operated, the air conditioning amplifier assembly receives a signal and operates the front seat heater.

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

• If the auxiliary battery voltage becomes low, auxiliary battery load control will operate in order to ensure sufficient power is supplied to the power steering system. In this case, the seat heater system (for HV model) may not operate.
• Inspect the fuses for circuits related to this system before performing the following procedure.

PROCEDURE

(a) Clear the DTCs.

Click here

NEXT

(a) Check for DTCs.

Click here

OK:

DTC B14B5 and B14C1 are not output.

NG

GO TO DIAGNOSTIC TROUBLE CODE CHART

OK

(a) Connect the Techstream to the DLC3.

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

(c) Turn the Techstream on.

(d) Enter the following menus: Body Electrical / Air Conditioner / Active Test.

(e) Perform the Active Test according to the display on the Techstream.

OK:

The seat heater operates normally.

OK

REPLACE SEAT HEATER SWITCH (RADIO AND DISPLAY RECEIVER ASSEMBLY)

NG

(a) Remove the front seatback heater assembly LH.

Click here

(b) Inspect the front seatback heater assembly LH.

Click here

NG

REPLACE FRONT SEATBACK HEATER ASSEMBLY LH

OK

(a) Disconnect the R26 front seat cushion heater assembly LH connector.

*a Front view of wire harness connector (to Front Seat Cushion Heater Assembly LH)

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

Standard Voltage:

Standard Resistance:

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

(a) Reconnect the R26 front seat cushion heater assembly LH connector.

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

(b) Disconnect the G37 air conditioning amplifier assembly connector.

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

Standard Voltage:

NG

GO TO STEP 8

OK

(a) Reconnect the G37 air conditioning amplifier assembly connector.

(b) Remove the air conditioning amplifier assembly with its connectors still connected.

Click here

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

Standard Voltage:

OK

REPLACE FRONT SEAT CUSHION HEATER ASSEMBLY LH

NG

REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY

(a) Disconnect the R26 front seat cushion heater assembly LH connector.

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

Standard Resistance:

OK

REPLACE FRONT SEAT CUSHION HEATER ASSEMBLY LH

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

Seat Heater for Front Right Seat does not Operate

DESCRIPTION

When the seat heater switch of the seat heater switch (radio and display receiver assembly) is operated, the air conditioning amplifier assembly receives a signal and operates the front seat heater.

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

• If the auxiliary battery voltage becomes low, auxiliary battery load control will operate in order to ensure sufficient power is supplied to the power steering system. In this case, the seat heater system (for HV model) may not operate.
• Inspect the fuses for circuits related to this system before performing the following procedure.

PROCEDURE

(a) Clear the DTCs.

Click here

NEXT

(a) Check for DTCs.

Click here

OK:

DTC B14B5 and B14C0 are not output.

NG

GO TO DIAGNOSTIC TROUBLE CODE CHART

OK

(a) Connect the Techstream to the DLC3.

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

(c) Turn the Techstream on.

(d) Enter the following menus: Body Electrical / Air Conditioner / Active Test.

(e) Perform the Active Test according to the display on the Techstream.

OK:

The seat heater operates normally.

OK

REPLACE SEAT HEATER SWITCH (RADIO AND DISPLAY RECEIVER ASSEMBLY)

NG

(a) Remove the front seatback heater assembly RH.

Click here

(b) Inspect the front seatback heater assembly RH.

Click here

NG

REPLACE FRONT SEATBACK HEATER ASSEMBLY RH

OK

(a) Disconnect the R6 front seat cushion heater assembly RH connector.

*a Front view of wire harness connector (to Front Seat Cushion Heater Assembly RH)

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

Standard Voltage:

Standard Resistance:

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

(a) Reconnect the R6 front seat cushion heater assembly RH connector.

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

(b) Disconnect the G37 air conditioning amplifier assembly connector.

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

Standard Voltage:

NG

GO TO STEP 8

OK

(a) Reconnect the G37 air conditioning amplifier assembly connector.

(b) Remove the air conditioning amplifier assembly with its connectors still connected.

Click here

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

Standard Voltage:

OK

REPLACE FRONT SEAT CUSHION HEATER ASSEMBLY RH

NG

REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY

(a) Disconnect the R6 front seat cushion heater assembly RH connector.

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

Standard Resistance:

OK

REPLACE FRONT SEAT CUSHION HEATER ASSEMBLY RH

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

System Description

SYSTEM DESCRIPTION

FRONT SEAT HEATER

(a) By operating the seat heater switch (radio and display receiver assembly), the temperature can be controlled within the range of 36 to 44°C (96.8 to 111.2°F).

HINT:

The operating temperature range is that detected by the thermistor, not at the seat surface.

(b) The seat heater switch (radio and display receiver assembly) indicator lights indicate seat heater operating status.

(c) The seat heaters of both seats are controlled by the seat heater control sub-assemblies.

REAR SEAT HEATER (w/ Rear Seat Heater)

(a) By operating the seat heater switch, the temperature can be controlled within the range of 36 to 44°C (96.8 to 111.2°F).

(b) The seat heater switch indicator lights indicate the seat heater operating status.

System Diagram

SYSTEM DIAGRAM

for Front Seat

for Rear Seat (w/ Rear Seat Heater)

Terminals Of Ecu

TERMINALS OF ECU

CHECK AIR CONDITIONING AMPLIFIER ASSEMBLY

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

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

HINT:

Measure the values on the wire harness side with the connector disconnected.

(c) Reconnect the G35 air conditioning amplifier assembly connector.

(d) Measure the voltage and check for pulses generation according to the value(s) in the table below.

CHECK SEAT HEATER SWITCH (RADIO AND DISPLAY RECEIVER ASSEMBLY)

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

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

HINT:

Measure the values on the wire harness side with the connector disconnected.

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

(d) Check for pulses according to the value(s) in the table below.