For 1990-2009 cars

### Description and Operation - Radio/Audio

Review the Radio/Audio Description and Operation section of this manual before proceeding with these diagnostic procedures. Refer to Radio/Audio System Description and Operation .

### Using a Test Antenna

Use a test mast antenna to quickly check for poor vehicle antenna operation. Unplug antenna lead-in connector from radio receiver and plug a test antenna into radio. Make sure the test antenna base is grounded to the vehicle chassis and keep hands off the mast. Check radio reception in an area away from electrical interferences. Tune to several weak and strong AM and FM stations. If the radio reception improved, the problem exists with the vehicle antenna and/or lead-in cable. If the reception is still poor, refer to Audio System Troubleshooting Hints .

### Antenna Ground Test

Important: Always zero out the DMM before taking a resistance measurement in order to ensure an accurate reading.

1. Disconnect the negative battery cable.
2. Disconnect the antenna lead-in connector from the radio receiver.
3. Measure the resistance from the negative battery cable to the coaxial cable, outer conductor, connector.
4. The resistance measured should be 0.20 ohms or less.
5. Test the following when the resistance is greater than 0.20 ohms.

• | Base of the antenna for a poor connection to body ground.

• | The coaxial cable interconnects for a poor connection or corrosion.

• | Test for an open or high resistance from the battery negative cable to the body. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

6. After finding and correcting the condition, operate the system in order to verify the repair.

### Antenna Coaxial Cable Testing

Use the appropriate chart and diagram to test the antenna coaxial cable resistances for the antenna system on the vehicle. Refer to the table when testing the antenna and/or lead-in cable.

#### Mast Antenna System

(1) | Negative Battery Cable
(2) | Coaxial Cable Conductor - Radio End
(3) | Coaxial Cable Metal Outer Shield - Radio End
(4) | Coaxial Cable Metal Outer Shield - Antenna End
(5) | Coaxial Cable Conductor - Antenna End
(6) | Antenna Base
(7) | Antenna Mast
(8) | Antenna Coaxial Cable

Ohmmeter Probes At Points | Resistance Measured In Ohms
--- | ---
1 and 3 | Less than 0.2
1 and 4 | Less than 0.2
1 and 6 | Less than 0.2
1 and 2 | Infinite
1 and 5 | Infinite
1 and 7 | Infinite
2 and 3 | Infinite
2 and 4 | Infinite
2 and 6 | Infinite
3 and 4 | Less than 0.2
3 and 6 | Less than 0.2
3 and 5 | Infinite
3 and 7 | Infinite

Important: Always zero out the DMM before taking a resistance measurement in order to ensure an accurate reading.

1. Measure the resistance from the coax center conductor to antenna mast, ohmmeter probes at points 2 and 7.
2. Total resistance from end to end of center conductor-ohmmeter probes at points 2 and 5:

• | RG-58/RG-59 type cable -- less than 0.20 ohms per foot

• | RG-62/RG-62M type cable -- less than 3.5 ohms per foot

3. When checking the resistance, cautiously wiggle the lead-in tip and cable. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
4. Replace the antenna and/or lead-in cable when the above readings are not obtained. Refer to Antenna Cable Replacement for service procedure.

#### On Board Diagnostics

Refer to On Board Diagnostics in Radio/Audio System Description and Operation for information on utilizing the Antenna Signal Strength Meter Mode for radio poor reception issues diagnosis.