B2476

DTC B2476

CIRCUIT DESCRIPTION
The OnStar(R) button assembly consists of 3 buttons, Call/Answer, OnStar(R) Call Center and OnStar(R) Emergency. 10 volts is supplied to the button assembly on the keypad supply voltage circuit. Each of the buttons, when pressed, completes the circuit across a resistor allowing a specific voltage to be returned to the vehicle communication interface module (VCIM) on the keypad signal circuit. Depending upon the voltage range returned, the VCIM is able to identify which button has been pressed.

DTC DESCRIPTOR
This diagnostic procedure supports the following DTC:
DTC B2476 Cellular Phone Select Service Switch Malfunction




This vehicle has DTCs which include DTC Symptoms. For more information on DTC Symptoms, refer to DTC Symptom Description in Vehicle DTC Information. DTC Symptom Description

CONDITIONS FOR RUNNING 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.
- All the above conditions are present for greater than 300 milliseconds.

CONDITIONS FOR SETTING THE DTC
- The VCIM powers the button assembly through the keypad supply voltage circuit for 11.5 ms, turns the power off, then waits for 50 ms and sees a voltage value greater than 1.8 volts on this circuit.
- The above conditions are present for greater than 300 milliseconds.

ACTION TAKEN WHEN THE DTC SETS
- The VCIM will ignore all inputs from the OnStar(R) button assembly.
- No calls can be placed.
- The OnStar(R) status LED turns red.

CONDITIONS FOR CLEARING THE DTC
- The VCIM powers the button assembly through the keypad supply voltage circuit for 11.5 ms, turns the power off, then waits for 50 ms and sees a voltage value less than 1.8 volts on this circuit.
- A history DTC clears after 50 malfunction free ignition cycles.
- The VCIM receives the clear DTC command from the scan tool.

TEST DESCRIPTION

Step 1 - Step 11:

The number below refers to the step number on the diagnostic table.
2. This step checks that the VCIM is sending out the proper supply voltage.