The radio is supplied with OnStar® a mono audio from vehicle communication interface module (VCIM). When the radio receives an audio signal from the VCIM the radio mutes the current audio signal and delivers an audio signal from the OnStar® system.

Schematic Reference

OnStar Schematics

Connector End View Reference

Entertainment/Communication Connector End Views

Description and Operation

OnStar Description and Operation

Electrical Information Reference

1. Ignition ON, radio ON, set volume to comfortable level and press OnStar Center Call button.
2. Verify Connecting to OnStar message is heard clearly through the audio system.

⇒	If OnStar message is not heard, go to Circuit/System Testing.

3. Tune radio to a known good station and verify that audio is heard clearly through all speaker channels.

⇒	If no, go to Speakers Inoperative - One or More .

4. If the radio is replaced, the new radio must have the setup procedure performed. Refer to Control Module References

Important: If the navigation mono audio signal low reference circuit is shorted to voltage the vehicle communication interface module (VCIM) has been damaged and requires replacement.

1. Disconnect connector C2 from VCIM.
2. Test for high resistance at the Cellular Telephone Voice signal circuit terminal 1 for an open or for a short to ground or for a short to voltage.
3. Test for a high resistance, or for a short to voltage at the Cellular telephone voice signal low reference circuit terminal 2 for an open.
4. If the circuits test normal, test or replace the VCIM.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.