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 communication interface module (CIM) 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 CIM on the signal circuit. The CIM provides a ground for the microphone via the low reference circuit.

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 (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 Testing

1. Ignition OFF, disconnect the harness connector at the cellular microphone.
2. Test for less than 10 Ohms between the low reference circuit terminal A and ground.

• If greater than the specified range, test the circuit for an open/high resistance.

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

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

4. If all circuits test normal, replace the cellular 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 CIM replacement, setup, and programming