B2455

DTC B2455

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) provide an overview of each diagnostic category.



DTC Descriptor
DTC B2455
- Cellular Phone Microphone Circuit Malfunction




Diagnostic Fault Information






Circuit/System Description

The vehicle communication interface module (VCIM) provides the cellular microphone with a supplied voltage on the cellular microphone signal circuit. When the microphone is in use, voice data from the user is sent back to the VCIM on the signal circuit. The VCIM provides a ground for the microphone via the low reference circuit.


Conditions for Running the DTC

* Ignition is in the RUN or ACC position.
* System voltage is 9.5-15.5 volts.
* The above conditions are present for greater than 10 seconds.



Conditions for Setting the DTC

* The VVCIM detects an open, short to ground or short to voltage in the cellular microphone signal circuit for greater than 10 seconds.
* The VVCIM detects an open/high resistance in the low reference circuit for greater than 10 seconds.



Actions Taken When the DTC Sets

* The OnStar(R) status LED turns red.
* The VCIM will not receive a signal from the microphone.
* Calls can be placed but the caller cannot be heard.



Conditions for Clearing the DTC

* The condition responsible for setting the DTC no longer exists.
* A history DTC will clear once 50 consecutive malfunction-free ignition cycles have occurred.


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 cellular phone microphone.
2. Ignition ON, test for 9.5-10.5 volts between the signal circuit terminal B and ground.

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

3. Test for 9.5-10.5 volts between the signal circuit terminal B and the low reference circuit terminal A.

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

4. If all circuit test normal, test or replace the cellular telephone microphone.



Repair Instructions

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

* Mobile Telephone Microphone Replacement (Service and Repair)
* Control Module References (Programming and Relearning) for VCIM replacement, setup, and programming