Buick Regal: OnStar Microphone Malfunction (IO5/IO6/IOB)

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.
• Refer to Diagnostic Procedure Instructions provide 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/System Description

The telematics communication interface control module provides the cellular phone microphone with a supplied voltage on the cellular phone microphone high 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 microphone low signal circuit.

Conditions for Running the DTC

• The Vehicle must be ON or in Service Mode.
• 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 s.

Conditions for Setting the DTC

B2455 02

The telematics communication interface control module detects a short to ground in the cellular phone microphone signal circuit for 10 s 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 s or greater.
• The telematics communication interface control module detects an open/high resistance in the low signal circuit for 10 s 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/Telematics Wiring Schematics

Connector End View Reference

Component Connector End View Index

Description and Operation

OnStar Description and Operation (UE1 with IOB/IO6) , OnStar Description and Operation (UI3) , or OnStar Description and Operation (UE1 without IOB/IO6).

Electrical Information Reference

• Refer to Circuit Testing
• Refer to Connector Repairs
• Refer to Testing for Intermittent Conditions and Poor Connections
• Refer to Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information.

Circuit/System Testing

1. Ignition OFF/Vehicle OFF, disconnect the harness connector at the B24 cellular phone microphone, Ignition ON/Vehicle in Service Mode.

2. Test for 8.0-10.5 V between the signal circuit terminal B and ground.

• If less than 8.0 V

1. Ignition OFF/Vehicle OFF, disconnect the X2 harness connector at the K73 telematics communication interface control module.
2. Test for infinite resistance between the signal circuit and ground.
   • If less than infinite resistance, repair the short to ground in the circuit.
   • Go to next step: If infinite resistance
3. Test for less than 2 Ω in the signal circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the vehicle K73 Telematics Communication Interface Control Module.

• If greater than 10.5 V

1. Ignition OFF/Vehicle OFF, disconnect the X2 harness connector at the K73 telematics communication interface control module, Ignition ON/Vehicle in Service Mode.
2. Test for less than 1 V between the signal circuit and ground.
   • If 1 V or greater, repair the short to voltage on the circuit.
   • Go to next step: If less than 1 V, replace the K73 Telematics Communication Interface Control Module.

• Go to next step: If between 9.5-10.5 V

3. Test for less than 1 V between the signal circuit terminal A and ground.

• If greater than 1 V

1. Ignition OFF/Vehicle OFF, disconnect the X2 harness connector at the K73 telematics communication interface control module, Ignition ON/Vehicle in Service Mode.
2. Test for less than 1 V between the signal circuit and ground.
   • If 1 V or greater, repair the short to voltage in the circuit.
   • If less than 1 V, repair the K73 Telematics Communication Interface Control Module.

• Go to next step: If less than 1 V

4. Test for greater than 8 V between the signal circuit terminal B and the signal circuit terminal A.

• If less than 8 V

1. Ignition OFF/Vehicle OFF, disconnect the connector X2 at the K73 telematics communication interface control module.
2. Test for infinite resistance between the low signal circuit and ground.
   • If less than infinite resistance, repair the short to ground in the circuit.
   • Go to next step: If infinite resistance
3. Test for less than 2 Ω in the signal circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the vehicle K73 Telematics Communication Interface Control Module.

• Go to next step: If greater than 8 V

5. Test or replace the B24 Cellular Phone Microphone.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

• Refer to Mobile Telephone Microphone Replacement
• Refer to Control Module References for telematics communication interface control module replacement, programming and setup.

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