Escalade EXT AWD V8-6.2L (2009)
Seat Heater: Description and Operation
Heated Seats Description and Operation (KA1)
Heated Seats Description and Operation (KA1)
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. During a cold ambient
remote start activation the heated seats will turn on.
Cadillac Switches
The heated seat switches are an integrated to the HVAC control head and when a heated seat switch is pressed 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 HVAC control head to display the heated seat indicators as necessary.
Chevrolet and GMC Switches
The heated seat switches are momentary contact switches and are inputs to the driver and passenger door lock/window switches. A ground circuit is
connected to the switch assembly through the door lock/window switch, and when a heated seat switch is pressed and released a brief switch signal is
supplied to the door lock/window 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 lock/window 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.