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.

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Antenna Enable Signal | 1 | 1 | -- | --
1. No or poor AM reception, amplifier inoperative (if equipped)

### Circuit/System Description

AM and FM radio reception is dependent on the following components:

• | Radio

• | Radio antenna

• | Coax cable between the radio and the radio antenna

The multi-band antenna is located on the roof of the vehicle. A switched B+ output from the radio antenna enable circuit is used to power the AM/FM portion of this antenna. The antenna enable circuit is also used to control the power state of the amplifier (if equipped) and the rear seat entertainment video display (if equipped).

### Diagnostic Aids

Poor AM and FM radio reception is dependent on multiple influences, some of which may not be vehicle related. Areas which have high RF traffic or block the signal path may cause a degradation in radio reception. Radio reception may also be influenced by items within the vehicle, but are not part of the radio system. Such examples are aftermarket electrical accessories or other items which may generate noise in the vehicle electrical system.

AM reception is highly dependent on the antenna receiving battery voltage from the radio. The antenna has a built in antenna amplifier that boosts both AM and FM reception. If the antenna does not receive battery voltage, the radio will still receive FM stations but AM stations will not be received.

### Reference Information

#### 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

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### Scan Tool Reference

Control Module References for scan tool information

### Circuit/System Verification

1. Inspect the antenna for proper mounting or physical damage.

⇒ | If damage is found, repair or replace as necessary

2. Radio ON, tune to several known strong FM, AM, and XM (if equipped) stations, and play a known good CD. Verify clear sound from all sources.

⇒ | If audio quality is poor from all sources, refer to Speaker Malfunction.

### Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the antenna.
2. Radio ON, verify that a test lamp illuminates between the signal circuit terminal 1 and ground.

⇒ | If test lamp does not illuminate, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the radio.

3. Ignition OFF, disconnect the radio antenna coax cable from the radio and the radio antenna.
4. Test for infinite resistance between the antenna coax center terminal and ground.

⇒ | If less than the specified value, replace the antenna coax.

5. Test for less than 10 Ω on the antenna coax center terminal from end to end.

⇒ | If greater than the specified range, replace the antenna coax.

6. Test for less than 10 Ω on the antenna coax outer shield from end to end.

⇒ | If greater than the specified range, replace the antenna coax.

7. Test for infinite resistance between the coax center terminal and the outer shield.

⇒ | If less than the specified value, replace the antenna coax.

8. If all circuits test normal, replace the radio antenna.

⇒ | If reception is still poor, replace the radio.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Antenna Cable Replacement

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