Seat Temperature Element: Testing and Inspection
SEAT HEATER SYSTEMINSPECTION
1. WIRING DIAGRAM
[Ref. to WI-127, WIRING DIAGRAM, Seat Heater System.] Diagrams By Diagram Name
2. DIAGNOSTIC CHART
3. CHECK SEAT HEATER FUSE
Remove the seat heater fuse and inspect visually. 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 seat heater switch.
2. Turn the ignition switch to ON.
3. Measure the voltage between harness connector terminal and chassis ground.
Connector & terminal
With SI-DRIVE
(C2) No. 12 (+) - Chassis ground (-):
Without SI-DRIVE
(C2) No. 11 (+) - Chassis ground (-):
Is the voltage 12 V or more?
- Yes -> Go to step 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
With SI-DRIVE
(C2) No. 2 - Chassis ground:
Without SI-DRIVE
(C2) No. 6 - Chassis ground:
Is the resistance less than 10 ohm?
- Yes -> Go to step 3.
- No -> Repair the harness.
3. Check ground circuit.
Measure the resistance between harness connector terminals.
Connector & terminal
With SI-DRIVE
(C2) No. 1 - (C2) No. 2:
(C2) No. 3 - (C2) No. 2:
Without SI-DRIVE
(C2) No. 3 - (C2) No. 6:
(C2) No. 7 - (C2) No. 6:
Is the resistance less than 10 ohm?
- Yes -> The power supply and ground circuit are normal.
- No -> Repair the harness.
5. CHECK THERMISTOR CIRCUIT
1. Disconnect the seat heater switch connector.
2. Measure the resistance between harness connector terminals.
Connector & terminal
Check LHD side
With SI-DRIVE
(C2) No. 8 - (C2) No. 3:
Without SI-DRIVE
(C2) No. 2 - (C2) No. 7:
Check RHD side
With SI-DRIVE
(C2) No. 6 - (C2) No. 1:
Without SI-DRIVE
(C2) No. 4 - (C2) No. 3:
Is the resistance between 1 K ohm to 200 K ohm?
- Yes -> The thermistor circuit is normal.
- No -> The harness or thermistor is faulty.
6. CHECK SEAT HEATER SWITCH
1. Check thermistor output voltage
1. Turn the ignition switch to ON.
2. Measure the voltage between the seat heater switch and chassis ground.
Connector & terminal:
LHD side seat
With SI-DRIVE
(C2) No. 8 (+) - Chassis ground (-):
Without SI-DRIVE
(C2) No. 2 (+) - Chassis ground (-):
RHD side seat
With SI-DRIVE
(C2) No. 6 (+) - Chassis ground (-):
Without SI-DRIVE
(C2) No. 4 (+) - Chassis ground (-):
Is the voltage 1.5 V or more?
- Yes -> Go to step 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
With SI-DRIVE
(C2) No. 9 (+) - Chassis ground (-):
Without SI-DRIVE
(C2) No. 1 (+) - Chassis ground (-):
RHD side seat
With SI-DRIVE
(C2) No. 7 (+) - Chassis ground (-):
Without SI-DRIVE
(C2) No. 9 (+) - Chassis ground (-):
Does the voltage fluctuate between 12 V and 0 V?
- Yes -> Harness faulty, open circuit of heater or thermostat faulty.
- No -> Replace the seat heater switch.