Circuit/System Description

WARNING: This page is about a different car, the 2017 GMC Acadia. However, it is still accessible from the selected car via links, so may be relevant.

The left and right rear heated seats switches are located with the auxiliary HVAC controls. When a heated seat switch is pressed, a serial data message is sent from the auxiliary HVAC controls to the body control module (BCM) indicating the rear heated seat command. The BCM serves as the heated seat system master to determine the requested operating mode. The BCM then sends a LIN bus serial data message to the rear seat heating control module indicating the heated seat command. In response to this message, the rear seat heating control module attempts to drive the appropriate seat heating elements per the BCM command. The BCM also controls the seat temperature and mode indicators, via the serial data line, used to provide the operator with feedback as to the operating status of the system.

The rear seat heating control module controls heated seat operation for the left and right rear seats. When active, power is applied to the seat cushion heater element through a pulse width modulated (PWM) voltage supply control circuit. The heater element is switched to ground by the module through a low side drive control circuit.

The seat cushion temperature sensor (thermistor) is packaged with the seat heating element located just under the seat cover. The rear seat heating control module supplies the temperature sensor with a 5 V reference signal circuit and a low reference circuit. The module monitors the voltage from the signal circuit to determine the temperature of the seat.

The temperature sensor varies in resistance based on the temperature of the heating element causing the signal voltage to change. Once the module senses the seat reached the set temperature, it will then begin regulate the current flow through the heater elements in order to maintain the desired seat temperature based on the feedback voltage from the sensor.