GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2007 🢒 Cobalt 🢒 Driver Information and Entertainment 🢒 Cellular, Entertainment, and Navigation 🢒 Radio Poor Reception

Diagnostic Instructions
    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provides an overview of each diagnostic category.

Circuit/System Description

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

    • Radio antenna
    • Coax cable between the radio antenna and the radio
    • Radio

Diagnostic Aids

Poor AM and FM radio reception is dependent on multiple influences, some of which may not be vehicle related. Areas which have high RF traffic or block the signal path may cause a degradation in radio reception. Radio reception may also be influenced by items within the vehicle, but not part of the radio system. Such examples are aftermarket electrical accessories or other items which may generated noise in the vehicle electrical system.

AM reception is highly dependent on the powered antenna receiving battery voltage from the radio. The powered antenna has a built in antenna amplifier that boosts both AM and FM reception. When the powered antenna no longer receives power, the radio will still receive FM stations and loose all AM stations.

Reference Information

Schematic Reference

Radio/Navigation System Schematics

Connector End View Reference

Entertainment/Communication Connector End Views

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

Scan Tool Data List

Circuit/System Verification

Inspect the antenna for damage.

⇒If damage found, replace as necessary.

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 Speakers Inoperative - One or More.
⇒If both AM and FM reception is poor, refer to Antenna Circuit Testing.

Circuit/System Testing

Antenna Circuit Testing

  1. Disconnect the antenna coax from the radio and the radio antenna.
  2. Test for infinite resistance between the antenna coax center terminal and ground.
    3. ⇒If less than the specified value, replace the antenna coax.
  3. Test for less than 5 ohms of resistance on the antenna coax center terminal from end to end.
    4. ⇒If greater than the specified range, replace the antenna coax.
  4. Test for less than 5 ohms of resistance on the antenna coax outer shield from end to end.
    5. ⇒If greater than the specified range, replace the antenna coax.
  5. Test for infinite resistance between the coax center terminal and the outer shield.
    6. ⇒If less than the specified value, replace the antenna coax.
  6. Reconnect the coax to the radio antenna. Test for infinite resistance on the coax at the radio between the center terminal and the outer shield.
    7. ⇒If less then specified value, replace the antenna.
  7. Ignition ON, radio ON, verify radio reception has improved.
    8. ⇒If there is still poor reception, replace the radio.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Control Module References for radio replacement, setup, and programming
    •  Radio Antenna Replacement