OnStar Microphone Malfunction
OnStar Microphone Malfunction
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.
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 signal circuit. When the cellular phone 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 microphone via the low reference wire.
Reference Information
Schematic Reference
OnStar Schematics OnStar Schematics
Connector End View Reference
Component Connector End Views Sunshade - Left Front
Description and Operation
OnStar Description and Operation OnStar
Electrical Information Reference
* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs
Scan Tool Reference
Control Module References Programming and Relearning for scan tool information
Circuit/System Verification
Note: It is necessary to have the vehicle in a quiet, open outside area where a cellular call can be successfully placed and GPS data can be received from satellites.
1. Ignition ON.
2. Verify that DTC B2455 is not set.
• If DTC B2455 is set
Refer to DTC B2455 B2455.
• If DTC B2455 is not set
3. Verify that your voice is heard clearly by the OnStar Call Center after completing a blue button press.
• If your voice can not be heard clearly
Refer to Circuit/System Testing.
• If your voice can be heard clearly
4. All OK.
Circuit/System Testing
1. Ignition OFF, disconnect the harness connector at the B24 cellular phone microphone, ignition ON.
2. Test for 9.5-10.5 V between the signal+ circuit terminal B and ground.
• If less than 9.5 V
1. Ignition 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.
• If infinite resistance
3. Test for less than 2 ohms in the signal+ circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, replace the vehicle K73 telematics communication interface control module.
• If greater than 10.5 V
1. Ignition OFF, disconnect the X2 harness connector at the K73 telematics communication interface control module, ignition ON.
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.
• If less than 1 V, replace the K73 telematics communication interface control module.
• If between 9.5-10.5 V
3. Ignition ON.
4. Test for less than 1 V between the signal- circuit terminal A and ground.
• If greater than 1 V
1. Ignition OFF, disconnect the X2 harness connector at the K73 telematics communication interface control module, ignition ON.
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.
• If less than 1 V
5. Test for 9.5-10.5 V between the signal+ circuit terminal B and the signal- circuit terminal A.
• If not between 9.5-10.5 V
1. Ignition OFF, disconnect the connector X2 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.
• If infinite resistance
3. Test for less than 2 ohms in the signal- circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, replace the K73 telematics communication interface control module.
• If between 9.5-10.5 V
6. Test or replace the B24 cellular phone microphone.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the repair.
* Mobile Telephone Microphone Replacement Service and Repair
* Control Module References Programming and Relearning for telematics communication interface control module replacement, programming and setup.