Heated Seats

Seats

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Principles of Operation

Heated Seats

The heated seat system operates independently from the climate control system and is controlled by the heated seat module located underneath the front passenger seat cushion. The heated seat buttons are part of the Front Controls Interface Module (FCIM) controls. When switched voltage is supplied and a heated seat button on the FCIM is pressed, a request message is delivered via CAN communication to the HVAC module. The HVAC module then provides a momentary ground to the heated seat module to command the system on or off.

The heated seat module supplies voltage to heater mats located in the seat cushion and backrest to heat the seat. The heated seat module regulates seat temperature by monitoring resistance of a thermistor type thermostat located in the cushion heater mat. The heated seat module is designed to remain on, heating the seat and maintaining temperature until switched off.

Normal heat cycle may require several minutes to initially warm the seat. The seat should be occupied to correctly test for normal operation. Temperature measuring devices do not provide an accurate method for testing heated seat operation as surface temperatures are subject to human and environmental characteristics. Correct testing requires heater mat resistance measurements which have tight tolerances affecting the length of time for the heater mats to reach maximum operating temperature.

The heated seat module monitors the heater output and thermistor circuits for fault detection but does not report DTCs and is not connected to the communication bus circuits. If an open circuit or short to ground occurs, the output is disabled to the heater mats and the heated seat indicators turn off. When a fault is detected the heated seat module only disables the affected seat and the other seat may continue to operate normally. The heated seat cannot be operated until the system is repaired and the ignition is cycled OFF and ON to reset the heated seat module from the detected fault.

The HVAC module monitors the control circuits to the heated seat module and will set a DTC if a circuit fault is detected. Refer to the HVAC Module DTC Chart. HVAC Module DTC Chart

The heated seat module is designed with an auto-configuration feature for use with heated seat systems on other vehicles equipped with dual contact switches. This feature enables additional input circuits not intended for use on this vehicle and will cause the heated seats to operate incorrectly. If this occurs, the heated seats will both display a symptom of operating only in one mode and illuminating only one indicator. If this condition exists, a reset procedure is required to correctly configure the heated seat module for use. For diagnosis of this condition, GO to Symptom Chart. Symptom Related Diagnostic Procedures