B2476

CIRCUIT DESCRIPTION
The OnStar button assembly consists of three buttons, Call/Answer, OnStar Call Center and OnStar Emergency. Ten volts is supplied to the button assembly on the keypad supply voltage circuit. Each of the buttons, when pressed, completes the circuit across a resister allowing a specific voltage to be returned to the VIU on the keypad signal circuit. Depending upon the voltage range returned, the VIU is able to identify which button has been pressed.

CONDITIONS FOR SETTING THE DTC
^ The ignition must be in the RUN or ACC position.
^ The system voltage is at least 9.5 volts and no more than 15.5 volts.
^ The keypad signal circuit voltage to the VIU is less than 2.8 volts or more than 3.2 volts.
^ All the above conditions are present for greater than 300 ms.

ACTION TAKEN WHEN THE DTC SETS
^ The VIU will ignore all inputs from the OnStar button assembly.
^ No calls can be placed.
^ The OnStar status LED turns RED.

CONDITIONS FOR CLEARING THE DTC
^ The keypad signal circuit voltage is between 2.8 volts and 3.2 volts.
^ A history DTC clears after 50 malfunction free ignition cycles.
^ The VIU receives the clear DTC command from the scan tool.

TEST DESCRIPTION

Steps 1-9:

The numbers below refer to the step numbers on the diagnostic table.
2. This step checks that the VIU is sending out the proper supply voltage.