Tahoe 2WD V8-5.3L (2007)
Seat Heater: Description and Operation
Heated Seats (Front)
HEATED SEATS DESCRIPTION AND OPERATION (FRONT)
DESCRIPTION
The driver and passenger heated seats have 2 heat zone operating modes with 3 heat level modes and will operate only while the engine is running.
The heat zones are determined by which of the 2 heated seat buttons are pressed, while the heat level is determined by the number of times they are
pressed. Pressing the seat cushion button 1 time will activate the seat back and cushion heater elements in the high mode. Each time the seat cushion
button is pressed the seat back and cushion heat level is reduced from high to medium, low, and off. Pressing the heated seat back button 1 time will
activate only the seat back heater element in the high mode. Each time the seat back button is pressed the seat back heat level is reduced from high to
medium, low, and off. During heated seat operation the heat zone operating mode may be changed without affecting the current heat level mode.
SWITCHES
The heated seat switches are momentary contact switches and are inputs to the driver and passenger door switches. A ground circuit is connected to
the switch assembly through the door switch, and when a heated seat switch is pressed and released a brief switch signal is supplied to the door switch.
Whenever the door module receives an active heated seat switch input, the active switch signal is sent to the memory seat module as a GMLAN
message. The memory seat module determines the heated seat mode based on the switch messages and sends a message to the door switch to display
the heated seat indicators as necessary.
HEATED SEAT OPERATION
The memory seat module controls the voltage supply and the ground circuits to the seat heater elements. When a heated seat function is commanded
active, the seat module will switch battery voltage to the heater element supply circuits, and ground is provided through pulse width modulation
(PWM) low side drive control circuits. During heated seat operation both the seat back and cushion heater elements are supplied battery voltage. The
seat module grounds the appropriate control circuits for back only or back and cushion heating modes, and opens or closes the active control circuits
as necessary in order to maintain the desired seat temperature. The seat module relies on 4 independent inputs from thermistors located in the seat
back and seat cushion of the driver and passenger seats to control heated seat temperatures. The thermistors are 2-wire sensors supplied with a 5-volt
referenced signal circuit and a low reference circuit from the seat module. Resistance through the thermistors varies with temperature causing the
heated seat sensor signal circuit voltage levels to decrease as the seat back temperatures rise. The seat modules allow heated seat operation only while
the engine is running which is determined by a GMLAN serial data circuit message.
