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.
Circuit/System Description
When an OnStar(R) keypress is made, a class 2 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 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 Verification
1. Tune radio to a known good station and verify the audio is heard clearly through all speaker channels.
• If audio is not heard clearly, refer toSpeaker Malfunction (Speaker Malfunction) .
2. Ignition ON, radio ON, set volume to comfortable level and press OnStar(R) Center Call button.
3. Verify Connecting to OnStar(R) message is heard clearly through the audio system.
• If OnStar(R) message is noisy or distorted, refer to Circuit/System Testing.
Circuit/System Testing
1. Ignition OFF, disconnect the X2 harness connector at the audio amplifier.
2. Ignition ON, test for a momentary AC voltage between the signal circuit terminal B12 and the signal circuit terminal A12 when the white dot button on the OnStar keypad is pressed.
• If a momentary AC voltage was not present, replace the VCIM.
3. Ignition OFF, disconnect the X2 harness connector at the VCIM.
4. Verify that a test lamp does not illuminate between B+ and the signal circuit terminal 1.
• If the test lamp illuminates, test the signal circuit for a short to ground.
5. Verify that a test lamp does not illuminate between B+ and the signal circuit terminal 2.
• If the test lamp illuminates, test the signal circuit for a short to ground.
6. Test for less than 1 ohm between the signal circuit terminal 1 and the audio amplifier X2 harness connector terminal B12.
• If greater than the specified range, test the signal circuit for a short to voltage or an open/high resistance.
7. Test for less than 1 ohm between the signal circuit terminal 2 and the audio amplifier X2 harness connector terminal A12.
• If greater than the specified range, test the signal circuit for a short to voltage or an open/high resistance.
8. If all circuits test normal, replace the VCIM.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
Control Module References (Programming and Relearning) for VCIM programming and setup