GM Service Manual Online
For 1990-2009 cars only

Heated Seat System

The heated seat system incorporates a heated seat switch, heated seat module, seat temperature sensor, heating elements in the seat cushion (front and rear) and heating elements in the seat back (front only). All the passengers seats (front and rear) have a seat belt switch that is used for an enable signal when the seat belt is buckled.

Front Heated Seat Description

The front Heated Seat Switches receive power, with the Ignition in the Run position, from the RR HVAC fuse in the I/P Fuse Block through CKT 341 (BRN). When the switch is placed in the LOW position, the ON signal is sent to the Heated Seat Module through CKT 1503 (PNK/BLK), and the HIGH/LOW Signal is sent through CKT 1505 (LT BLU/BLK) to the heated seat module. The low side of the Heated Seat Switch has approximately 275ohms of resistance, while the high side has approximately 310ohms of resistance. The Heated Seat Module receives battery voltage from the FRONT HEATED SEATS fuse, in the underhood fuse block, through CKT 1840 (ORN). With the heated seat switch on, battery voltage is sent from the module through CKT 1462 (LT BLU) to the Seat Cushion Element. Output is sent through CKT 1985 (PPL) to the Seat Back Element. Since the elements are connected in series, ground for both elements is provided through CKT 150 (BLK) to ground G202. The temperature sensors for the seats are located with the seat cushion element. The sensor monitors seat temperature and a varying resistance that is monitored at the Signal Enable, cavity E of the Heated Seat Module. The Heated Seat Module compares this signal to the HI/LO input to determine when to apply and shut off battery voltage to the heating elements. Temperature settings are maintained around:

    • 37.5°C (98.5°F) for the LOW position.
    • 42.5°C (107.5°F) for the HIGH position.

Both the Driver's and Passenger's, heated seats operate the same. However, the Passenger's seat needs seat belt buckled. When the seat belt is not buckled, the enable signal through CKT 182 (YEL) is grounded at the heated seat module and the system will not operate.

Rear Heated Seat Description

The Rear Heated Seat Switches, like the front, receive power, with the Ignition in the Run position, from the RR HVAC fuse in the I/P Fuse Block through CKT 341 (BRN). These switches are mounted in the center floor console, giving access to the rear passengers. When the switch is in the LOW position, the ON signal is sent through CKT 901 (GRY), and the HIGH/LOW signal is sent through CKT 902 (PPL) to the Heated Seat Module. Resistance in the switch in the LOW position is approximately 200ohms and in the HIGH position is approximately 310ohms. Both rear heated seat modules receive constant power from the Heated Seats Rear fuse located in the Underhood Fuse-Relay Center through CKT 1940 (ORN). When the Heated Seat Module receives a signal from the Heated Seat Switch, CKT 1460 (PPL) (LR)/CKT 902 (PPL) (RR), the Module sends power to the LED, CKT 903 (DK GRN) (LR)/CKT 900 (DK GRN), located in the switch letting the passenger know that the heated seat control is on. The seat belt switch for both rear passenger seats operates the same as the front passengers. The belt must be buckled in order for the heated seat module to receive the ungrounded signal from the seat temperature sensor. When the module receives the signal it then compares the signal to the HI/LOW signal sent to the module from the heated seat switch through CKT 1464 (GRY) (LR)/CKT 901 (GRY) (RR) to determine the proper seat temperature setting.

The rear seats have the same temperature settings as the front. However, the rear seats only have seat cushion elements.