Circuit/System Description
WARNING: This page is about a different car, the 2010 GMC Sierra, 2010 GMC Cab & Chassis Sierra, 2010 Chevrolet Silverado, and 2010 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
The front seat heating elements are controlled by a common high current relay internal to the heated seat module (HSM) and on the low side by individual element control circuits. The HSM connects the seat heater element supply voltage circuits to a common reference point. This reference point is biased to approximately 2.5 V. Before the HSM will allow heated seat operation, it checks to see if the heating element supply voltage circuits and control circuits are shorted to ground or battery voltage. Once the HSM verifies that it is not closing to a shorted heating element, it allows heated seat operation. After which it continues to monitor for a shorted circuit.