Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual: Seat Heater for Front Left Seat does not Operate

Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual / Vehicle Interior / Seat / Seat Heater System / Seat Heater for Front Left Seat does not Operate

DESCRIPTION

When the refreshing seat switch (for front side) is operated, the air conditioning amplifier assembly receives the signal. The air conditioning amplifier assembly receives the signal and operates the front seat heater.

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

  • If the battery voltage is low, the seat heater system may not operate. When "Operation of Electrical Items Restricted." is displayed on the multi-information display in the combination meter assembly, inspect the battery, referring to On-vehicle Inspection for the charging system.

    Click here

  • If the battery voltage is low, the seat heater system may not operate. When "Operation of Electrical Items Restricted." is not displayed on the multi-information display in the combination meter assembly, check the Data List item "Battery Control Count (Body ECU)".

    Click here

  • 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 or B14C1 is not output.

Result

Proceed to

OK (for Standard Seat Type)

A

OK (for Sports Seat Type)

B

NG

C
B

GO TO STEP 7

C

GO TO DIAGNOSTIC TROUBLE CODE CHART

A

3.

CHECK HARNESS AND CONNECTOR (IG POWER SUPPLY - FRONT SEAT CUSHION HEATER LH (SEAT HEATER ASSEMBLY) - BODY GROUND)

(a) Disconnect the c8 front seat cushion heater LH (seat heater assembly) connector.

*a

Front view of wire harness connector

(to front seat cushion heater LH (seat heater assembly))

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

Standard Voltage:

Tester Connection

Condition

Specified Condition

c8-3 (IG) - Body ground

Engine switch on (IG)

11 to 14 V

c8-3 (IG) - Body ground

Engine switch off

Below 1 V

c8-1 (B) - Body ground

Always

11 to 14 V

Standard Resistance:

Tester Connection

Condition

Specified Condition

c8-2 (E) - Body ground

Always

Below 1 Ω
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

4.

INSPECT FRONT SEAT CUSHION HEATER LH (SEAT HEATER ASSEMBLY)

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

Click here

(b) Inspect the front seat cushion heater LH (seat heater assembly).

Click here

NG

REPLACE FRONT SEAT CUSHION HEATER LH (SEAT HEATER ASSEMBLY)

OK

5.

INSPECT FRONT SEATBACK HEATER LH (SEAT HEATER ASSEMBLY)

(a) Remove the front seatback heater LH (seat heater assembly).

Click here

(b) Inspect the front seatback heater LH (seat heater assembly).

Click here

NG

REPLACE FRONT SEATBACK HEATER LH (SEAT HEATER ASSEMBLY)

OK

6.

CHECK HARNESS AND CONNECTOR (AIR CONDITIONING AMPLIFIER ASSEMBLY - FRONT SEAT CUSHION HEATER LH (SEAT HEATER ASSEMBLY))

(a) Disconnect the J42 and J48 air conditioning amplifier assembly connectors.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

J48-15 (SHD+) - c8-5 (SWR)

Always

Below 1 Ω

J48-15 (SHD+) or c8-5 (SWR) - Body ground

Always

10 kΩ or higher

J48-17 (TSL) - c8-6 (THR)

Always

Below 1 Ω

J48-17 (TSL) or c8-6 (THR) - Body ground

Always

10 kΩ or higher

J42-8 (SG-5) - c8-4 (PR)

Always

Below 1 Ω

J42-8 (SG-5) or c8-4 (PR) - Body ground

Always

10 kΩ or higher
OK

GO TO STEP 11

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

7.

CHECK HARNESS AND CONNECTOR (IG POWER SUPPLY - FRONT SEAT CUSHION HEATER (FRONT SEAT CUSHION PAD WITH COVER LH) - BODY GROUND)

(a) Disconnect the c8 front seat cushion heater (front seat cushion pad with cover LH) connector.

*a

Front view of wire harness connector

(to front seat cushion heater (front seat cushion pad with cover LH))

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

Standard Voltage:

Tester Connection

Condition

Specified Condition

c8-3 (IG) - Body ground

Engine switch on (IG)

11 to 14 V

c8-3 (IG) - Body ground

Engine switch off

Below 1 V

c8-1 (B) - Body ground

Always

11 to 14 V

Standard Resistance:

Tester Connection

Condition

Specified Condition

c8-2 (E) - Body ground

Always

Below 1 Ω
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

8.

INSPECT FRONT SEAT CUSHION HEATER (FRONT SEAT CUSHION PAD WITH COVER LH)

(a) Remove the front seat cushion heater (front seat cushion pad with cover LH).

Click here

(b) Inspect the front seat cushion heater (front seat cushion pad with cover LH).

Click here

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

9.

INSPECT FRONT SEATBACK HEATER (FRONT SEATBACK PAD WITH COVER LH)

(a) Remove the front seatback heater (front seatback pad with cover LH).

Click here

(b) Inspect the front seatback heater (front seatback pad with cover LH).

Click here

NG

REPLACE FRONT SEATBACK HEATER (FRONT SEATBACK PAD WITH COVER LH)

OK

10.

CHECK HARNESS AND CONNECTOR (AIR CONDITIONING AMPLIFIER ASSEMBLY - FRONT SEAT CUSHION HEATER (FRONT SEAT CUSHION PAD WITH COVER LH))

(a) Disconnect the J42 and J48 air conditioning amplifier assembly connectors.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

J48-15 (SHD+) - c8-5 (SWR)

Always

Below 1 Ω

J48-15 (SHD+) or c8-5 (SWR) - Body ground

Always

10 kΩ or higher

J48-17 (TSL) - c8-6 (THR)

Always

Below 1 Ω

J48-17 (TSL) or c8-6 (THR) - Body ground

Always

10 kΩ or higher

J42-8 (SG-5) - c8-4 (PR)

Always

Below 1 Ω

J42-8 (SG-5) or c8-4 (PR) - Body ground

Always

10 kΩ or higher
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

11.

REPLACE SEAT HEATER CONTROL SUB-ASSEMBLY LH

(a) Temporarily replace the seat heater control sub-assembly LH with a new or known good one.

Click here

NEXT

12.

CHECK SEAT HEATER OPERATION

(a) Check the seat heater.

Click here

OK:

The seat heater operates normally.

OK

END (SEAT HEATER CONTROL SUB-ASSEMBLY LH WAS DEFECTIVE)
NG

13.

REPLACE REFRESHING SEAT SWITCH (FOR FRONT SIDE)

(a) Temporarily replace the refreshing seat switch (for front side) with a new or known good one.

Click here

NEXT

14.

CHECK SEAT HEATER OPERATION

(a) Check the seat heater.

Click here

OK:

The seat heater operates normally.

OK

END (REFRESHING SEAT SWITCH (FOR FRONT SIDE) WAS DEFECTIVE)
NG

REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY

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