Radio Poor Reception
Radio Poor Reception
Antenna System Test
The length of the antenna coax cable lead-in and antenna body determines the total system ground measurement.
Important: Always zero out the DMM before taking a resistance measurement in order to ensure an accurate reading.
1. Disconnect the antenna lead-in connector from the radio receiver.
2. Measure the resistance from the negative battery post to the coax outer conductor connector.
3. The resistance measured should be as follows:
* Cable less than 5 ft-No more than 0.035 ohms
* Cable 5-13 ft-No more than 0.060 ohms
* Cable 13-20 ft-No more than 0.085 ohms
4. Test the following when the resistance is greater than specified:
* 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 Diagnostic Aids. Component Tests and General Diagnostics
* Do not use black (phosphate-coated) hardware for antenna mounting purposes. This type of fastener is unreliable in making good connections.
5. After finding and correcting the condition, operate the system in order to verify the repair.
Perform the Antenna Checking Procedures after confirming the integrity of the antenna ground.
Antenna Checking Procedures
Perform the following tests for the type of antenna on the vehicle.
Using a Test Antenna
Use a test mast antenna to check for poor vehicle antenna operation. Unplug antenna lead-in connector from radio receiver and plug the 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. Audio System Troubleshooting Hints
Antenna Coaxial Cable Testing
Disconnect the antenna coax cable connector from the radio receiver and perform the following measurements.
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 cable center conductor to center conductor or antenna mast.
2. Total resistance from end to end of center conductor:
* RG-58/RG-59 type cable-Less than 0.20 ohms
* RG-62/RG-62M type cable-Less than 3.5 ohms
3. When checking the resistance, cautiously wiggle the lead-in tip and cable. Refer to Testing for Intermittent Conditions and Poor Connections in Diagnostic Aids. Component Tests and General Diagnostics
4. Measure the resistance from the cable center conductor to metal case. Reading should be infinite.
5. Replace the antenna and/or lead-in cable when the above readings are not obtained.
Radio Antenna Module System
Important: The following information lists the most probable cause of the concern to the least probable cause followed by the appropriate test for that condition. If the test leads to the replacement of a component, always inspect for a poor connection before proceeding with the replacement. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Diagnostic Aids. Component Tests and General Diagnostics
This antenna system consists of an antenna module and a mast antenna.
Perform the Antenna System Test and test the antenna coax cable prior to performing the following tests:
* The radio antenna module is not grounded properly. The module grounding screws should be clean and tight. Measure the resistance from the antenna module base plate to a good ground. Resistance should be 0.020 ohms or less. Find and correct the condition if the resistance is out of specification.
* The antenna module supply voltage circuit to the radio antenna module is open or shorted to ground. Test the antenna module supply voltage circuit for an open or short to ground. Refer to Circuit Testing and Wiring Repairs in Diagnostic Aids. Component Tests and General Diagnostics
* No antenna module supply voltage output from the radio. Disconnect the radio antenna module connector. Turn ON the radio and measure the voltage from the antenna module supply voltage circuit of the radio to a good ground. Voltage measured should be near 12 volts. If no voltage is measured, replace the radio. Refer to Radio Replacement for service procedure. Perform the VIN Relearn procedure after replacing the radio. On the scan tool, go to Module Replacement/Setup in Vehicle Control Systems and select Radio.
* Defective radio antenna module. Replace the radio antenna module.
* After finding and correcting the condition, operate the system in order to verify the repair.