The vehicle navigation radio and OnStar® system both utilize the cellular microphone to receive voice commands. The navigation radio receives an audio voice signal from the communication interface module (CIM).

Schematic Reference

Radio/Navigation System Schematics

Connector End View Reference

Entertainment/Communication Connector End Views

Description and Operation

Radio/Audio System Description and Operation

Electrical Information Reference

Scan Tool Reference

Scan Tool Data List

Ignition ON, verify the OnStar® voice recognition is operating normally.

1. Ignition OFF, disconnect the C2 harness connector at the CIM.
2. Ignition ON, test for 8.5-9.5 volts between the cellular microphone signal circuit terminal 2 and ground.

⇒	If less than specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the radio.

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

3. Ignition OFF, test for less than 10 ohms between the cellular microphone low reference circuit terminal 4 and ground.

⇒	If greater than 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. Ignition OFF, disconnect the C1 harness connector at the radio.
5. Verify that a test lamp does not illuminate between B+ and the cellular microphone low reference circuit terminal 9.

⇒	If the test lamp illuminates, test the low reference circuit for a short to ground.

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

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for Radio or CIM replacement, setup, and programming