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DTC B2455

DTC B2455

Diagnostic Instructions


• Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• Diagnostic Procedure Instructions provides an overview of each diagnostic category.


DTC Descriptors

DTC B2455 02

Cellular Phone Microphone Circuit Short to Ground

DTC B2455 04

Cellular Phone Microphone Circuit Open

Diagnostic Fault Information

Circuit Short to Ground Open/High Resistance Short to Voltage Signal Performance
Cellular Microphone Signal B2455 02 B2455 04 - -
Cellular Microphone Low Reference - B2455 04 1 -
1. OnStar Microphone Inoperative - Caller Cannot Be Heard


Circuit/System Description

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

Conditions for Running the DTC


• The ignition must be in the RUN or ACC position.

• The system voltage is at least 9.5 V and no more than 15.5 V.

• All the above conditions are present for greater than 10 seconds.


Conditions for Setting the DTC

B2455 02

The telematics communication interface control module detects an short to ground in the cellular phone microphone signal circuit for 10 seconds or greater.

B2455 04

The following conditions will set this DTC:


• The telematics communication interface control module detects an open/high resistance in the cellular phone microphone signal circuit for 10 seconds or greater.

• The telematics communication interface control module detects an open/high resistance in the low reference circuit for 10 seconds or greater.


Action Taken When the DTC Sets


• The OnStar® status LED turns red.

• The telematics communication interface control module will not receive a signal from the cellular phone 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.


Reference Information

Schematic Reference

OnStar Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

OnStar Description and Operation

Electrical Information Reference


• Circuit Testing

• Connector Repairs

• Testing for Intermittent Conditions and Poor Connections

• Wiring Repairs


Scan Tool Reference

Control Module References for scan tool information

Circuit/System Testing


1. Ignition OFF, disconnect the harness connector at the B24 cellular phone microphone.

2. Ignition ON, test for 9.5-10.5 V between the signal circuit terminal B and ground.

3. If less than the specified range, test the circuit for a short to ground, shorted together, or an open/high resistance. If the circuit tests normal, replace the K73 telematics communication interface control module.

4. If greater than the specified range, test the circuit for a short to voltage. If the circuit tests normal, replace the K73 telematics communication interface control module.

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

6. If less than the specified range, test the low reference circuit for a short to ground, shorted together, or an open/high resistance. If the circuit tests normal, replace the K73 telematics communication interface control module.

7. If greater than the specified range, test the low reference circuit for a short to voltage. If the circuit tests normal, replace the K73 telematics communication interface control module.

8. If all circuit test normal, replace the B24 cellular phone microphone.


Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.


• Mobile Telephone Microphone Replacement

• Control Module References for telematics communication interface control module replacement, setup, and programming