According to the service manual, The factory installed two front heated seat switches are momentary, push button-type switches, that provide a request signal to the Heated Seat Module (HSM) (also know as the comfort seat wheel module), over the Controller Area Network (CAN) bus, signaling the HSM to energize the heating element for the selected seat. Light Emitting Diodes (LED) in each switch indicate the level of heat in use. The front seat switch LEDs are controlled by the HSM.
The factory installed Heated Seat Module (HSM) is located under the front passenger seat. The HSM is a microprocessor designed to use the Controller Area Network (CAN) data bus messages from the A/C-heater control to operate the front heated seats. When equipped with rear heated seats, the HSM receives request signals from the rear heated seat switches over hard-wired circuits.
Doesn't look like you can use the dash switches without also installing a HSM and perhaps a vehicle computer update.
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