Circuit/System Description
WARNING: This page is about a different car, the 2020 Cadillac CT4. However, it is still accessible from the selected car via links, so may be relevant.
The OnStar® button assembly consists of 3 buttons: Call/Answer, OnStar® Call Center, and OnStar® Emergency. The K73 Telematic Control Module supplies the OnStar® button assembly with 10 V via circuit 2515. Each of the buttons, when pressed, completes the circuit across a resistor allowing a specific voltage to be returned to the K73 Telematic Control Module over the keypad signal circuit 2514. Depending upon the voltage range returned, the K73 Telematic Control Module is able to identify which button has been pressed.