The driver and passenger heated seats each consist of the following
components:
• | Seat Cushion Heating Element |
• | Seat Back Heating Element |
The body control module (BCM) is also involved in the operation of the
heated seats.
Power and Grounds
Battery positive voltage is applied to both front heated seat modules
from the rear fuse block IGN SEN Fuse. This allows the heated seats to operate
only when the ignition is in the ON position. Battery positive voltage is
also supplied at all times to the heated seat modules from the rear fuse block;
HTDST L Fuse for the driver heated seat module, or, HTDST R
for the passenger heated seat module. Both modules are grounded through the
ground circuit to G201. The driver and passenger heated seat switches are
both grounded through the switch ground circuits to G201
Heated Seats & LED Indicators
The driver and passenger heated seats are controlled by separate heated
seat switches. When a heated seat switch is pressed once, the temperature
is set to high heat and the module applies a low voltage through the heated
seat high temperature indicator control circuit to illuminate the high heat
indicator. When the switch is pressed a second time, the temperature is set
to low heat and the module turns off the high heat indicator. The module then
applies a low voltage through the heated seat low temperature indicator control
circuit to illuminate the low heat indicator. During high or low heat, the
module applies battery positive voltage through the heated seat
element supply voltage circuit to the seat cushion and seat back heating elements.
After the switch is pressed a third time, the module removes the voltage from
the low heat indicator and the heating elements turning off the indicator
and the heated seat. The heated seat module will also disable the heated seats
when the ignition switch has been turned to the OFF position.
Temperature Regulation
The heated seat system is designed in order to warm the seat cushion
and seat back to approximately 42°C (107.6°F) when in the high position,
and 37°C (98.6°F) when in the low position. The heated seat module
monitors the seat temperature through the temperature sensor signal circuit
and the temperature sensor (thermistor) that is located in the seat cushion.
The temperature sensor is a variable resistor, it's resistance changes as
the temperature of the seat changes. When the temperature sensor resistance
indicates to the heated seat module that the seat has reached the desired
temperature, the module opens the path to ground from the heating elements.
The module will then cycle the controlled ground open and closed in order
to maintain the desired temperature.
Load Management
The load management feature controls the amount of power consumed in
the vehicle under heavy power load demands. If the vehicle demands high power
for over 2 minutes, the body control module (SBM) commands the heated
seat module through the inhibit signal circuit to cycle the power output
to the heater elements at approximately 50% of normal capacity. The load
management feature occurs under the following conditions:
• | The blower is set to the HIGH position. |
• | The headlamps are in the ON position. |
• | The rear window defroster is in the ON position. |
• | One of the heated seats is in the ON position. |
Due to the load management function, customers may complain that the
heated seats do not warm up quickly or warm at a lower temperature than normal.
Deactivating one of the above systems will deactivate the load management
function.