Refer to “Seat Heater System” in the wiring diagram. 
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.
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.