Circuit/System Description

The OnStar® talk switch, if equipped, is incorporated with the headlamp switch. The body control module supples a B+ input signal to the switch. When the switch is pressed, the signal is pulled low through the switch to the headlamp switch low reference circuit in the body control module. When the body control module senses the signal is pulled low, a serial data message is sent to the communication interface module to start voice interaction with the OnStar® system.