Schematic Reference:
Radio/Audio System Schematics
Diagnostic System Check - Vehicle
Always perform the Diagnostic System Check - Vehicle before proceeding
with these diagnostic procedures. Refer to
Diagnostic System Check - Vehicle .
Antenna System Test
Important: Always zero out the DMM before taking a resistance measurement in order to ensure
an accurate reading.
- Disconnect the negative battery cable.
- Disconnect the antenna lead-in connector from the radio receiver.
- Measure the resistance from the negative battery cable to the coax outer
conductor connector.
- The resistance measured should be 0.20 ohms or less.
- Test the following when the resistance is greater than 0.20 ohms.
| • | The coaxial cable interconnects for a poor connection or corrosion. |
- 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.
Diversity Antenna System
Important: This diversity antenna system is comprised of 3 antennas in the decklid
liner assembly 2 radio antenna modules, a coax, and an FM composite signal
from the radio to the right antenna module. In AM and WX mode the system functions
as follows:
The right antenna module takes the signal from only the AM/FM1 antenna. The
right antenna module amplifies this signal and sends it to the radio. In this mode,
the right antenna module sends 8 volts to power the left antenna module via
a coax.
In FM mode the system functions as follows:
The left antenna module takes the signal from the FM2 antenna and sends it to
the right antenna module where it is mixed with the signal from the FM1 antenna. The
right antenna module combines and amplifies both signals and sends it to the radio.
In this mode the radio supplies 5-8 volts over the FM composite signal
wire and this switches the modules into FM mode. The right antenna module sends 8 volts
to power the left antenna module via coax. The FM composite signal also provides a
feedback signal to the right antenna module, which indicates the quality of the signal.
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.
Perform the Antenna System Test and test the antenna coax cable prior to performing
any of the following tests.
Poor Reception on Both AM and FM Bands
| • | The radio antenna modules are not grounded properly. The module grounding
screws should be clean and tight. The antenna module grounds are either a chassis
ground or a ground strap. Measure the resistance from the antenna module base plate
to a good ground. Resistance should be 0.20 ohms or less. Find and correct
the condition if the resistance is out of specification. |
| • | The coax between the left and right antenna modules is open or shorted
to ground or short to B+. Test for 8 volts from the center conductor of the
coax from the right antenna module. If the voltage is not within or near the specified
value, test the coax for an open or short for ground or short to B+. Refer to
Circuit Testing and
Wiring Repairs. |
| • | The FM composite signal circuit to the radio antenna module is open, shorted
to ground, or shorted to B+. Test the FM composite signal circuit for an open or short
to ground. Refer to
Circuit Testing and
Wiring Repairs. |
| • | Defective antenna module--Replace the antenna module. Refer to
Control Module References for replacement, setup, and programming. |
Poor Reception on AM Band Only
| • | Defective Right Antenna Module--Replace the right antenna module.
Refer to
Control Module References for replacement, setup, and programming. |
Poor Reception on FM Band Only
| • | Defective Right Antenna Module, no 8-volt--Replace the right antenna
module. Refer to
Control Module References for replacement, setup, and programming. |
| • | Defective left or right antenna module--Replace the antenna module.
Refer to
Control Module References for replacement, setup, and programming. |
