Heated Seat System Operation

WARNING: This page is about a different car, the 2003 GMC Sierra, 2003 GMC Cab & Chassis Sierra, 2003 Chevrolet Silverado, and 2003 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

The driver and passenger heated seats are controlled by the driver seat module using inputs from the heated seat switches and the seat back temperature sensors and will operate only while the engine is running. The heated seat switches are inputs to the driver and passenger door modules which provide the heated seat switch information to the driver seat module through Class 2 serial data circuit messages. The heated seat operating mode off, high, medium, or low is determined by the number of times the heated seat switch is pressed. Pressing the heated seat switch 1 time will activate the seat back and cushion heater elements in the high mode, and each time the switch is pressed during an ignition cycle the seat back and cushion heat level is reduced from high to medium, low, and off.

The heated seat switches are momentary contact type switches and are supplied with battery voltage from the door modules. When a heated seat switch is pressed and released a brief switch signal voltage is supplied to the door module. Whenever the door module receives an active heated seat switch input, the next heated seat operating mode is determined by whatever the current mode may be. The driver and passenger seat heater elements are controlled by the driver seat module. When activating any of the heated seat operating modes, the seat module switches battery voltage to the heater element supply circuits. All of the seat heater elements are grounded by the driver seat module through individual low side drive control circuits. The heater element low side control circuits are pulse width modulated to ground by the driver seat module and are used to control the seat temperatures by regulating the current flow through the heater elements. The driver seat module relies on inputs from thermistors installed in the driver and passenger seat backs in order to regulate the heated seat temperatures. The thermistors are 2 wire sensors supplied with a 5-volt referenced signal circuit and a low reference circuit from the driver seat module. Resistance through the thermistors varies with temperature causing the heated seat sensor signal circuit voltage levels to increase as the seat back temperatures rise. The driver seat module will allow heated seat operation only while the engine is running which is determined by a Class 2 serial data circuit message from the powertrain control module.