For 1990-2009 cars

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• | Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• | Diagnostic Procedure Instructions provides an overview of each diagnostic category.

### Circuit/System Description

The vehicle navigation system utilizes the cellular microphone to receive voice commands. The cellular microphone is wired directly to the navigation radio and consist of a 9-volt signal circuit and a low reference circuit.

### Reference Information

#### 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

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### Scan Tool Reference

Scan Tool Data List

### Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the cellular microphone.
2. Ignition ON, test for 8.5-9.5 volts between the cellular microphone signal circuit terminal B 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 A 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 low reference circuit terminal A.

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

6. If all circuits test normal, replace the cellular microphone.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Mobile Telephone Microphone Replacement

• | Control Module References for Radio replacement, setup and programming