B2476

DTC B2476

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
* Review Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

DTC B2476.00
- Cellular Phone Select Service Switch Malfunction

Circuit/System Description

The OnStar(R) button assembly consists of 3 buttons, Call/Answer, OnStar(R) Call Center and OnStar(R) 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 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.

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.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the inside rearview mirror.
2. Ignition ON, test for 9.8-10.2 volts between keypad supply voltage terminal 12 and ground.

• If less than the specified range, test the keypad supply voltage circuit for an open/high resistance or a short to ground. If the circuit tests normal, test or replace the VCIM.

• If greater than the specified range, test the keypad supply voltage circuit for a short to voltage. If the circuit tests normal, test or replace the VCIM.

3. If the circuit tests normal, replace the inside rearview mirror.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests

* Rearview Mirror Replacement
* Programming and Relearning Programming and Relearning