No (or Noisy) OnStar Audio

No (or Noisy) OnStar Audio

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
* Review Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions provides an overview of each diagnostic category.

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 antenna and cellular antenna coax.

Circuit/System Testing

1. Ignition OFF, disconnect the X2 harness connector at the VCIM.
2. Ignition ON, test for 30-40 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.
^ 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.

3. Test for 30-40 mV AC between the signal circuit terminal 1 and the low reference circuit terminal 2.

^ If not within the specified range, test the low reference circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the radio.

4. If all circuits test normal, replace the VCIM.

Repair Instructions

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