No (or Noisy) OnStar Audio

No (or Noisy) OnStar Audio

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) provides an overview of each diagnostic category.



Diagnostic Fault Information






Circuit/System Description

When an OnStar(R) keypress is made, a serial data message is sent to the audio system to mute all radio functions and transmit OnStar(R) originated audio. After the audio system is muted, the OnStar(R) signals are transmitted to the audio system on the cellular telephone voice signal circuit, and returned to the module on the cellular telephone voice low reference circuit. The cellular modem connects the OnStar(R) system to the cellular carriers communication system by interacting with the national cellular infrastructure. The module sends and receives all cellular communications over the cellular/navigation antenna and cellular antenna coax.


Reference Information
Schematic Reference

Radio/Navigation System Schematics (Radio/Navigation System 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 X2 harness connector at the CIM.
2. Ignition ON, test for less than 5 mV AC between the signal circuit terminal 1 and ground.

• If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the radio.

3. Install a DMM between the signal circuit terminal 1 and ground. Set the DMM to capture AC voltage using the MIN MAX function.
4. Press the voice recognition button. Verify the DMM captured greater than 20 mV AC.

• 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 radio.

5. Install a DMM between the signal circuit terminal 1 and the low reference circuit terminal 2. Set the DMM to capture AC voltage using the MIN MAX function.
6. Press the voice recognition button. Verify the DMM captured greater than 20 mV AC.

• If less than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the radio.

7. If all circuits test normal, replace the CIM.



Repair Instructions

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


Control Module References (Programming and Relearning) for CIM or Radio replacement, setup, and programming