Onstar® Button Assembly

WARNING: This page is about a different car, the 2003 GMC Sierra, 2003 GMC Cab & Chassis Sierra, 2003 Chevrolet Silverado, and 2003 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

The Onstar® button assembly may be part of the rear view mirror on some vehicles or a separate unit on others. The button assembly is comprised of three buttons and a status LED. The buttons are defined as follow:

The Answer/End Call button, which is black with a white dot allows the user to answer and end calls or initiate the personal calling feature, if equipped.
The blue Onstar® Call Center button, which displays the Onstar® logo, allows the user to connect to the Onstar® call center.
The Emergency button, which will display either a red or white cross, sends a high priority emergency call to the Onstar® call center when pressed.

The Onstar® button assembly receives ten volts on the keypad supply voltage circuit. When pressed, each button completes a circuit across a resistor allowing a specific voltage to be returned to the VCIM on the keypad signal circuit. Depending upon the voltage range returned, the VCIM is able to identify which button has been pressed.

The Onstar® button assembly status LED is green when the system is on and operating normally. When the status LED is green and flashing, it is an indication that a call is in progress. When the LED is red, this indicates a system malfunction is present. The Onstar® LED is controlled by the VCIM over the keypad red LED signal circuit and the keypad green LED signal circuit.