Diversity Antenna 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 INTERMITTENT OR POOR CONNECTIONS  and  CONNECTOR REPAIRS  in Wiring Systems.

This antenna system uses two antennas to form a diversity system. The primary antenna is part of the rear window. The primary antenna receives both AM and FM signals. The secondary antenna is located on the passenger side of the windshield. The secondary antenna receives only FM signals. The radio antenna module processes the antenna reception signals and phase aligns them to create one strong signal.

Perform the Antenna System Test and test the antenna coax cable prior to performing the following tests.

1. 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 0.20 ohms or less. Find and correct the condition if the resistance is out of specification.
2. The antenna enable signal circuit to the radio antenna module is open or shorted to ground. Test the antenna enable signal circuit for an open or short to ground.
3. The FM composite signal circuit to the radio antenna module is open or shorted to ground. or short to ground.
4. Improper retention of the antenna cable in the floating retainer. Poor or no connection with the radio will result when the radio is installed if the antenna cable is not properly attached in the floating retainer. Inspect the antenna cable for movement in the floating retainer. Replace the antenna cable if movement is found. Refer to ANTENNA CABLE REPLACEMENT   for service procedure.
5. Defective radio antenna module. Replace radio antenna module.
6. No FM composite signal voltage output from the radio. Disconnect the radio antenna module connector. Turn ON the radio and tune the radio to the FM band. Measure the voltage from the FM composite signal circuit of the radio antenna module to a good ground. Voltage measured should be near 8 V. If no voltage is measured, replace the radio, Refer to RADIO REPLACEMENT   for service procedure.
7. After finding and correcting the condition, operate the system in order to verify the repair.
   Fig 1: Radio Controls Inoperative - Rear Seat (with UK6) Diagnostic Chart (1 Of 2)

   Courtesy of GENERAL MOTORS CORP.
   Fig 2: Radio Controls Inoperative - Rear Seat (with UK6) Diagnostic Chart (2 Of 2)

   Courtesy of GENERAL MOTORS CORP.
   Fig 3: Rear Seat Audio Power Indicator Always On (with UK6) Diagnostic Chart (1 Of 2)

   Courtesy of GENERAL MOTORS CORP.
   Fig 4: Rear Seat Audio Power Indicator Always On (with UK6) Diagnostic Chart (2 Of 2)

   Courtesy of GENERAL MOTORS CORP.
   Fig 5: Tape Player Weak, Slow, or Garbled Output Diagnostic Chart

   Courtesy of GENERAL MOTORS CORP.
   Fig 6: Steering Wheel Controls Inoperative Diagnostic Chart (1 Of 2)

   Courtesy of GENERAL MOTORS CORP.
   Fig 7: Steering Wheel Controls Inoperative Diagnostic Chart (2 Of 2)

   Courtesy of GENERAL MOTORS CORP.