The vehicle navigation radio and Onstar® system (If equipped) both utilize the cellular microphone located on the inside rearview mirror to receive voice commands. The navigation radio receives an audio voice signal from the communication interface module (CIM). If the vehicle is not equipped with Onstar®, the microphone is connected only to the navigation radio.

Schematic Reference

Radio/Navigation System Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Radio/Audio System Description and Operation

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

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

With UE1

1. Ignition OFF, disconnect the X3 harness connector at the CIM.
2. Ignition ON, test for 8.5-9.5 volts between the navigation voice 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 ON, test for less then 1 volt between the navigation voice low reference circuit terminal 4 and ground.

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

4. Ignition OFF, test for less than 10 ohms between the navigation voice low reference circuit terminal 4 and ground.

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

5. Ignition ON, test for 8.5-9.5 volts between the navigation voice signal circuit terminal 2 and the ground.

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

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

Without UE1

1. Ignition OFF, disconnect the harness connector at the inside rearview mirror.
2. Ignition ON, test for 8.5-9.5 volts between the cellular microphone signal circuit terminal 10 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 ON, test for less then 1 volt between the terminal 2 and ground.

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

4. If all circuits test normal, replace the inside rearview mirror assembly.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.