B2476

DTC B2476 or B2482

Diagnostic Instructions

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



DTC Descriptors
DTC B2476
- Cellular Phone Select Service Switch

DTC B2482
- Cellular Phone Select Service Switch Range/Performance




Diagnostic Fault Information






Circuit/System Description

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


Conditions for Running the DTC

* Ignition ON.
* Battery voltage is between 9-16 volts.



Conditions for Setting the DTC

DTC B2476

The VCIM detects a short to voltage, short to ground, or an open/high resistance on the keypad 10 volt reference circuit.

DTC B2482

The VCIM detects a valid signal on the keypad signal circuit for longer than 15 seconds. If one of the OnStar(R) buttons is held or stuck for 15 seconds or greater, the VCIM will set this DTC.


Action Taken When the DTC Sets

* The OnStar(R) status LED turns red.
* No calls can be placed.
* The VCIM will ignore all inputs from the OnStar(R) button assembly.



Conditions for Clearing the DTC

* The condition responsible for setting the DTC no longer exists.
* A history DTC will clear once 100 consecutive malfunction-free ignition cycles have occurred.



Reference Information
Schematic Reference

OnStar Schematics (OnStar Schematics)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

OnStar Description and Operation (OnStar Description and Operation)
Electrical Information Reference

* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information


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 the 10 volt reference circuit terminal 12 and ground.

• If greater than the specified range, test the 10 volt reference circuit for a short to voltage. If the circuit tests normal, replace the VCIM.
• If less than the specified range, test the 10 volt reference circuit for a short to ground or open/high resistance. If the circuit tests normal, replace the VCIM.

3. Test for 0 volts between the signal circuit terminal 11 and ground.

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

4. Test for 9.8-10.2 volts between the 10 volt reference circuit terminal 12 and the signal circuit terminal 11.

• If less than the specified range, test the keypad signal circuit for an open/high resistance. If the circuit tests normal, replace the VCIM.

5. Ignition OFF, disconnect the X1 harness connector at the VCIM.
6. Test for infinite resistance between the signal circuit terminal 11 and ground.

• If less than the specified range, test the signal circuit for a short to ground.

7. If all circuits test normal, test or replace the inside rearview mirror.



Component Testing

1. Ignition OFF, disconnect the harness connector at the inside rearview mirror .
2. Test for infinite resistance between the supply voltage terminal 12 and the signal terminal 11.

• If not the specified value, replace the inside rearview mirror.

3. Test for 1.4k-1.6k ohms between the supply voltage terminal 12 and the signal terminal 11 while pressing the black Call/Answer button.

• If not within the specified range, replace the inside rearview mirror.

4. Test for 2.7k-3.3k ohms between the supply voltage terminal 12 and the signal terminal 11 while pressing the blue On-Star(R) button.

• If not within the specified range, replace the inside rearview mirror.

5. Test for 11.7k-14.3k ohms between the supply voltage terminal 12 and the signal terminal 11 while pressing the red emergency button.

• If not within the specified range, replace the inside rearview mirror.




Repair Instructions

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

* Inside Rearview Mirror Replacement (Inside Rearview Mirror Replacement)
* Control Module References (Programming and Relearning) for VCIM replacement, setup, and programming