GM Service Manual Online
For 1990-2009 cars only

The heated seat module receives battery voltage at all times from the PWR/HEATED SEAT circuit breaker. When the heated seat switch is pressed, the heated seat module receives ignition voltage, through the switch, from the HVAC/DIC/DRL/HEATED SEAT fuse. The temperature sensor inside the seat cushion heater pad senses the temperature of the cushion and signals the temperature control unit to increase or decrease the amount of current to the seat cushion and seat back heater elements.