Seat Temperature Element: Testing and Inspection
INSPECTION
1. WIRING DIAGRAM
Refer to "Seat Heater System" in the wiring diagram. [Ref. to WIRING DIAGRAM, Seat Heater System.] Electrical Diagrams
2. DIAGNOSTIC CHART
- STI model
- Except for STI model
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 circuit.
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 connector 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 connector terminal and chassis ground.
Connector & terminal
(AD8) No. 2 - Chassis ground:
Is the resistance less than 10 ohms?
- 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 ohms?
- Yes -> The power supply and ground circuit are normal.
- No -> Replace the seat heater switch.
5. CHECK THERMISTOR CIRCUIT
Measure the resistance between harness connector 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 k ohms and 200 k ohms?
- 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 heater 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 heater 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 connector.
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 malfunction, 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 module of seat cushion side.
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 connector 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 connector terminal and chassis ground.
Connector & terminal
(R42) No. 3 - Chassis ground:
(R43) No. 3 - Chassis ground:
Is the resistance less than 10 ohms?
- 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 ohms?
- 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.