Heated Seat Switch/LED Indicators and System Operation without A45

WARNING: This page is about a different car, the 2016 GMC Acadia, 2016 Chevrolet Traverse, and 2016 Buick Enclave. However, it is still accessible from the selected car via links, so may be relevant.

Battery voltage is supplied at all times to the heated seat module (HSM) from the HTD/SEAT fuse located in the I/P fuse block. Battery voltage from the BCM is supplied to both heated seat switches with the ignition ON. Ground for both heated seat switches is supplied at G302 while ground for the HSM is supplied at G303.

The following describes the sequence of operation and how the HSM responds to each of the switch inputs.

High Temperature-When the heated seat switch is pressed once, ground is applied through the switch contacts and the switch signal circuit to the HSM indicating the high heat request. In response to this signal, the HSM applies battery voltage through the heating element supply voltage circuit and ground through the element low reference circuits to the seat cushion and seat back heating elements. At the same time, the HSM applies a low current voltage through the 3 temperature indicator control circuits illuminating all 3 LEDs indicating the high temperature mode.
Medium Temperature-When the switch is pressed a second time, the HSM sets the temperature level to medium heat and removes the voltage from the high temperature indicator leaving 2 LEDs illuminated indicating the medium temperature mode.
Low Temperature-When the switch is pressed a third time, the HSM sets the temperature level to low heat and removes the voltage from the medium temperature indicator leaving 1 LED illuminated indicating the low temperature mode.
System OFF State-When the switch is pressed a fourth time, the HSM removes the battery voltage and grounds from the heating elements and the voltage from the low temperature indicator, indicating the system OFF state.
Back Only Mode-When the heated seat is ON and the BACK ONLY mode button is pressed, ground is applied through the switch contacts and the heated seat back only mode signal circuit to the HSM. In response to this signal, the HSM opens the ground path to the seat cushion heater element, leaving just the seat back heater active. At the same time, the HSM turns OFF the seat cushion/back mode indicator, then applies a low current voltage through the heated seat back only mode indicator control circuit illuminating the back only mode indicator.