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

A diversity antenna system is designed to deliver the best radio signal reception possible. Two antennas are used to form a diversity system. The primary antenna is part of the right rear quarter window. This antenna receives both AM and FM signals. The secondary antenna is part of the left rear quarter window and receives only FM signals for the audio system. RFA signals are also received by this antenna module.

The antenna reception signals are sorted out by the radio antenna modules. The radio antenna modules are enabled when the radio is turned on. When the AM or FM band is selected on the radio, the antenna modules connects the rear window antenna directly to the radio. In addition, when the FM band is selected an enable signal is sent to the right antenna module. Superimposed on this enable signal is the strength of the signal being received by the radio tuner. The antenna module performs two functions: it switches between the left and right antennas, monitoring the radio signal strength and combines both signals and phase aligns them to create one strong signal.

The left antenna module receives the FM2 signal from the left rear quarter glass and passes this signal to the right antenna module. The right antenna module receives the FM1 signal from the right rear quarter glass where it then combines the two signals to be sent to the radio via coax. The right antenna module is powered by the left antenna module via the FM2 signal coax. The FM composite signal from the radio provides feedback of signal quality to the right antenna module. This signal is 5-8 volts when in FM mode and 0v when in AM.

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

1. Inspect the antennas located in the left and right rear windows. Verify all branches of the antennas are intact, with no scratches or other damage.

⇒	If damage is found, repair or replace as necessary

2. Radio ON, tune to several known FM, AM, and XM (if equipped) stations, and play a known good CD.

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

1. Inspect the radio antennas and antenna leads for damage.

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

2. Inspect each radio antenna module grounding surface and the mounting hardware for any corrosion that may cause a poor ground.

⇒	If corrosion is noted, clean the grounding surfaces and hardware.

3. Ignition OFF, disconnect the X1 harness connector at the left radio antenna module.
4. Radio ON, test for B+ between the signal circuit terminal 1 and ground.

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

5. Ignition OFF, connect the harness connector at the left antenna module.
6. Disconnect the X1 harness connector at the right antenna module.
7. Radio tuned to FM, test for 4.5 - 8.5 volts on the FM composite signal terminal 1.

⇒	If less than specified range, test the signal circuit for a short to ground. If the circuit tests normal, replace the radio.

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

8. Radio tuned to AM, test for less than 1 volt on the FM composite signal terminal 1

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

9. Ignition OFF, connect the harness connector at the right antenna module.
10. Disconnect the coax cable from the left antenna module.
11. Ignition ON, radio tuned to FM, test for 4.5 - 8.5 volts between the center terminal and the outer shield.

⇒	If greater than the specified range, test the coax for a short to voltage. If the circuit tests normal, replace the right antenna module.

⇒	If less than specified range, test the coax for a short to ground or an open/high resistance. If the circuit tests normal, replace the right antenna module.

12. Ignition ON, radio tuned to AM, test for less than 1 volt between the center terminal and the outer shield.

⇒	If greater than the specified range, test the coax for a short to voltage. If the circuit tests normal, replace the right antenna module.

Note: For steps 13-17, perform the tests on the disconnected coax cable between the radio and the right antenna module.

13. Ignition OFF, disconnect the coax cable at the radio and right antenna module.
14. Test for infinite resistance between the antenna coax center terminal and ground.

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

15. Test for less than 5 ohms on the antenna coax center terminal from end to end.

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

16. Test for less than 5 ohms on the antenna coax outer shield from end to end.

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

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

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

18. Replace the left antenna module. Radio ON, verify the radio reception has improved.

⇒	If there is still poor reception, replace the right antenna module. If there is still poor reception, replace the radio.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.