Heated Seats

Heated Seats Description and Operation

Heated Seat Components

The driver and passenger heated seat system consists of the following components:

* Heated seat switch

* Door lock/window switch

* Memory seat module (factory installed system)

* Heated seat module (dealer installed system)

* Seat cushion heating element

* Seat back heating element

* Seat cushion temperature sensor

* Seat back temperature sensor

Modes of Operation

The memory seat module (MSM)/heated seat module (HSM) controls heated seat operation for both the driver and passenger seats. There are 2 modes of operation available for heated seats; both the seat cushion and seat back heat, or seat back only heat. When a heated seat temperature signal request is received, the MSM/HSM will activate both the seat cushion and seat back heating elements. When the heated seat BACK ONLY mode button is pressed once the MSM/HSM will deactivate the seat cushion heating element and leave the seat back heating element ON.

Factory Installed Heated Seat System Operation

The driver and passenger heated seats are controlled by separate heated seat switches located in the door panels. Ground is supplied to the heated seat switches through the switch low reference circuits from their respective door lock/window switches. The door lock/window switches also control the heated seat switch heat mode and temperature indicators. The memory seat module (MSM) controls the heated seat operation for both front heated seats.

The following describes the sequence of operation and how the MSM responds to each of the switch inputs.

* High Temperature-When the heated seat switch is pressed once, ground is applied through the switch contacts and the switch signal circuit to the door lock/window switch indicating the high heat request. In response to this signal, the door lock/window switch applies a low current voltage through the 3 temperature indicator control circuits illuminating all 3 LEDs indicating the high temperature mode. The switch then sends a message via the GMLAN serial data line to the MSM indicating the heated seat request. The MSM then applies battery voltage through the heating element supply voltage circuit to the seat cushion and seat back heating elements. At the same time, it supplies a ground through the element low reference circuits to the seat heating elements.

* Medium Temperature-When the switch is pressed a second time, the MSM sets the temperature level to medium heat. The door lock/window switch removes the voltage from the high temperature indicator leaving 2 LEDs illuminated indicating the medium temperature mode.

* Low Temperature-When the switch is pressed a third time, the MSM sets the temperature level to low heat. The door lock/window switch removes the voltage from the medium temperature indicator leaving 1 LED illuminated indicating the low temperature mode.

* System OFF State-When the switch is pressed a fourth time, the MSM removes the battery voltage and grounds from the heating elements. The door lock/window switch removes the voltage from the low temperature indicator, indicating the system OFF state.

* Back Only Mode-When the heated seat is ON and the BACK ONLY mode button is pressed, ground is applied through the switch contacts and the heated seat back only mode signal circuit to the door lock/window switch. In response to this signal, the door lock/window switch sends a GMLAN message to the MSM indicating the back only mode request. The MSM then opens the ground path to the seat cushion heater element, leaving the seat back heater active. The door lock/window switch turns OFF the seat cushion/back mode indicator, then applies a low current voltage through the heated seat back only mode indicator control circuit illuminating the back only mode indicator.

Dealer Installed Heated Seat System Operation

The dealer installed driver and passenger heated seats are controlled by separate heated seat switches located in the instrument panel trim plate on the right side of the HVAC controls.

The following describes the sequence of operation and how the heated seat module (HSM) responds to each of the switch inputs.

* High Temperature-When the heated seat switch is pressed once, ground is applied through the switch contacts and the switch signal circuit to the HSM indicating the high heat request. In response to this signal, the HSM applies battery voltage through the heating element supply voltage circuit and ground through the element low reference circuits to the seat cushion and seat back heating elements. At the same time, the HSM applies a low current voltage through the 3 temperature indicator control circuits illuminating all 3 LEDs indicating the high temperature mode.

* Medium Temperature-When the switch is pressed a second time, the HSM sets the temperature level to medium heat and removes the voltage from the high temperature indicator leaving 2 LEDs illuminated indicating the medium temperature mode.

* Low Temperature-When the switch is pressed a third time, the HSM sets the temperature level to low heat and removes the voltage from the medium temperature indicator leaving 1 LED illuminated indicating the low temperature mode.

* System OFF State-When the switch is pressed a fourth time, the HSM removes the battery voltage and grounds from the heating elements and the voltage from the low temperature indicator, indicating the system OFF state.

* Back Only Mode-When the heated seat is ON and the BACK ONLY mode button is pressed, ground is applied through the switch contacts and the heated seat back only mode signal circuit to the HSM. In response to this signal, the HSM opens the ground path to the seat cushion heater element, leaving just the seat back heater active. At the same time, the HSM turns OFF the seat cushion/back mode indicator, then applies a low current voltage through the heated seat back only mode indicator control circuit illuminating the back only mode indicator.

Temperature Regulation

The heated seat system is designed to warm the seat cushion and seat back to 3 different temperature settings; High, MED, and Low. The MSM/HSM monitors the seat temperature through the temperature sensor signal circuits and the temperature sensors (thermistor) that are located in the seat cushion and the seat back. The temperature sensors are variable resistors, their resistance varies as the temperature of the seat changes. When the temperature sensor resistance indicates to the MSM/HSM that the seat has reached the desired temperature, the module opens the ground path of the seat heating elements through the heated seat element control circuit. The module will then cycle the element control circuit open and closed in order to maintain the desired temperature.

Heated Seat Operation with Remote Vehicle Start

The heated seats will turn ON with a remote start only with cooler outside air temperatures and if the vehicle is equipped with an automatic climate control system.

When the remote start button is pressed and the HVAC control module senses cooler outside air temperatures, it sends a serial data message to the MSM commanding it to activate the heated seats. The heated seats will stay ON for approximately 10 minutes or until the ignition is turned to the ON/RUN position. Once the ignition is turned to the ON/RUN position the heated seats will have to be manually turned ON and OFF.

Load Management

The electrical power management function is designed to monitor the vehicle electrical load and determine when the battery is potentially in a high discharge condition. The heated seat system is one of the vehicle loads that is subject to reduction during a battery discharge condition. For more information on load management refer to Electrical Power Management Description and Operation (Diesel) Description and OperationElectrical Power Management Description and Operation (Gasoline) Description and Operation.