GM Service Manual Online
For 1990-2009 cars only

Battery positive voltage is supplied at all times to the heated seat module from the HTD SEAT fuse located in the rear fuse block. Ignition voltage is supplied to the heated seat switch and the heated seat module from the ROOF/HEAT SEAT fuse located in the BCM. When commanded ON, the heated seat module uses this voltage to heat the seat heating elements. The heated seat module and the seat heating elements are grounded through the module ground circuit to G303.

Each time the heated seat switch is pressed, B+ is supplied to the heated seat module through the heated seat signal circuit. The module counts these inputs to determine what level of heat the vehicle operator is commanding. In response to these switch signals, the heated seat module closes it's contacts and applies battery positive voltage through the heated seat element supply voltage circuit to the seat heating elements. When the thermistor inside the seat cushion reaches a certain resistance, the control module open and close the supply voltage in order to maintain that heat level.