Subaru Impreza 3 / Impreza WRX / Impreza WRX STI. Manual — part 712

SE-17

Seat Heater System

SEATS

4. Seat Heater System

A: REMOVAL

1. SEAT HEATER MODULE

1) Remove the front seats. <Ref. to SE-6, REMOV-

AL, Front Seat.>

2) Remove the backrest cover of front seat and

seat cushion cover. <Ref. to SE-6, DISASSEM-

BLY, Front Seat.>

3) Remove the seat heater module.

2. SEAT HEATER SWITCH

1) Remove the console box. <Ref. to EI-51, RE-

MOVAL, Console Box.>

2) Remove the seat heater switch from the console

box.

B: INSTALLATION

Install each part in the reverse order of removal.

C: INSPECTION

1. WIRING DIAGRAM

Refer to “Seat Heater System” in the wiring dia-

gram. <Ref. to WI-88, WIRING DIAGRAM, Seat

Heater System.>

2. DIAGNOSTIC CHART

• Models with SI-DRIVE

• Models without SI-DRIVE

3. CHECK SEAT HEATER FUSE

Remove the seat heater fuse, and then visually

check.

Is the fuse blown out?

• Yes → Replace the fuse.

• No → Check the power supply and ground cir-

cuit.

SE-00082

Symptoms

Repair order

Seat heater does not
operate.

1. Check the fuse. <Ref. to SE-17,

CHECK SEAT HEATER FUSE,

INSPECTION, Seat Heater Sys-

tem.>

2. Check the seat heater system
power supply and ground circuit.

<Ref. to SE-18, CHECK POWER

SUPPLY AND GROUND CIR-

CUIT, INSPECTION, Seat Heater

System.>

3. Check the thermistor circuit.

<Ref. to SE-18, CHECK THER-

MISTOR CIRCUIT, INSPECTION,

Seat Heater System.>

4. Check the seat heater switch

circuit. <Ref. to SE-18, CHECK

SEAT HEATER SWITCH,

INSPECTION, Seat Heater Sys-

tem.>

5. Check the seat heater module.

<Ref. to SE-18, CHECK SEAT

HEATER MODULE, INSPEC-

TION, Seat Heater System.>

Symptoms

Repair order

Seat heater does not
operate.

1. Check the fuse. <Ref. to SE-17,

CHECK SEAT HEATER FUSE,

INSPECTION, Seat Heater Sys-

tem.>

2. Check the seat heater system
power supply and ground circuit.

<Ref. to SE-19, CHECK POWER

SUPPLY AND GROUND CIR-

CUIT, INSPECTION, Seat Heater

System.>

3. Check the seat heater switch

circuit. <Ref. to SE-19, SEAT
HEATER SWITCH, INSPEC-
TION, Seat Heater System.>

4. Check the seat heater module.

<Ref. to SE-18, CHECK SEAT

HEATER MODULE, INSPEC-

TION, Seat Heater System.>

SE-18

Seat Heater System

SEATS

4. CHECK POWER SUPPLY AND GROUND

CIRCUIT

1) CHECK POWER SUPPLY CIRCUIT.

(1) Disconnect the connector of seat heater

switch.

(2) Turn the ignition switch to ON.

(3) Measure the voltage between harness con-

nector terminal and chassis ground.

Connector & terminal

(AD8) No. 12 (+) — Chassis ground (–):

Is the voltage 12 V or more?

• Yes → Go to symptom 2.

• No → Check the harness between the seat

heater switch and fuse.

2) Check ground circuit

Measure the resistance between harness connec-

tor terminal and chassis ground.
Connector & terminal

(AD8) No. 2 — Chassis ground:

Is the resistance less than 10 Ω?

• Yes → Go to symptom 3.

• No → Repair the harness.

3) Check ground circuit

Measure the resistance between seat heater

switch terminals.
Connector & terminal

(AD8) No. 1 — (AD8) No. 2:

(AD8) No. 3 — (AD8) No. 2:

Is the resistance less than 10 Ω?

• Yes → The power supply and ground circuit are

normal.

• No → Replace the seat heater switch.

5. CHECK THERMISTOR CIRCUIT

Measure the resistance between harness connec-

tor terminals.
Connector & terminal

Check LHD side

(AD8) No. 8 — (AD8) No. 3:

Check RHD side

(AD8) No. 6 — (AD8) No. 1:

Is the resistance between 1 kΩ and 200 kΩ?

• Yes → Thermistor circuit is normal

• No → Harness faulty or thermistor faulty

6. CHECK SEAT HEATER SWITCH

1) Check thermistor output voltage.

(1) Connect the seat heater switch connector.

(2) Turn the ignition switch to ON.

(3) Measure the voltage between the seat heat-

er switch and chassis ground.

Connector & terminal:

LHD side seat

(AD8) No. 8 (+) — Chassis ground (–):

RHD side seat

(AD8) No. 6 (+) — Chassis ground (–):

Is the voltage 1.5 V or more?

• Yes → Go to symptom 2.

• No → Replace the seat heater switch.

2) Check output voltage.

(1) Turn the ignition switch to ON.

(2) Measure the voltage between the seat heat-

er switch and chassis ground when turning the

switch to a position other than OFF.

Connector & terminal:

LHD side seat

(AD8) No. 9 (+) — Chassis ground (–):

RHD side seat

(AD8) No. 7 (+) — Chassis ground (–):

Does the voltage repeat 12 V ←→ 0 V?

• Yes → The harness or thermistor is faulty, or

the heater has an open circuit.

• No → Replace the seat heater switch.

7. CHECK SEAT HEATER MODULE

1) Disconnect the seat heater module connector,

and check the continuity between terminals of con-

nector.
Connector & terminal

No. 1 — No. 3:

No. 1 — No. 4:

No. 3 — No. 4:

Is there continuity between connector terminals?

•

Continuity exists. →

Seat heater module is normal. If there is a malfunc-

tion, check the seat heater switch and vehicle body

side harness.

•

Continuity does not exist. →

No. 1 — No. 3: → Go to step 2).

No. 1 — No. 4: → Go to step 2).

No. 3 — No. 4: → Replace the seat heater mod-

ule of seat cushion side.

SE-00765

1

2

3

4

SE-19

Seat Heater System

SEATS

2) Disconnect the seat heater module of backrest

side, and check the continuity between connector

terminals of the seat heater module unit of backrest

side.

Is there continuity between connector terminals?

•

Continuity exists. →

Replace the seat heater module of seat cushion

side.

•

Continuity does not exist. →

Replace the seat heater module of backrest side.

8. CHECK POWER SUPPLY AND GROUND

CIRCUIT

1) Check power supply circuit.

(1) Disconnect the connector of seat heater

switch.

(2) Turn the ignition switch to ON.

(3) Measure the voltage between harness con-

nector terminal and chassis ground.

Connector & terminal

(R42) No. 2 (+) — Chassis ground (–):

(R43) No. 2 (+) — Chassis ground (–):

Is the voltage 12 V or more?

• Yes → Go to symptom 2.

• No → Check the harness between the seat

heater switch and fuse.

2) Check ground circuit.

Measure the resistance between harness connec-

tor terminal and chassis ground.
Connector & terminal

(R42) No. 3 — Chassis ground:

(R43) No. 3 — Chassis ground:

Is the resistance less than 10 Ω?

• Yes → Go to symptom 3.

• No → Repair the harness.

3) Check ground circuit.

Measure the resistance between seat heater

switch terminals.
Connector & terminal

(R42) No. 2 — (R42) No. 3:

(R43) No. 2 — (R43) No. 3:

Is the resistance less than 10 Ω?

• Yes → The power supply and ground circuit are

normal.

• No → Replace the seat heater switch.

9. SEAT HEATER SWITCH

1) Inspect the continuity between the seat heater

switch terminals.

Connector & terminal

HI

No. 2 — No. 1:

No. 2 — No. 3:

No. 1 — No. 3:

No. 4 — No. 3:

LOW

No. 2 — No. 4:

No. 2 — No. 3:

No. 4 — No. 3:

2) If no continuity exists, replace the seat heater

switch with a new part.

SE-01206

1

2

SE-00857

1

2

3

4

SE-20

Seat Heater System

SEATS