GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2008 🢒 Corvette 🢒 Diagnostic Navigation 🢒 Vehicle Diagnostic Information 🢒 Speaker Malfunction

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.

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Audio Amplifier B+

2, 3

2, 3

--

--

Antenna Enable Signal

2, 3

2, 3

2, 3

--

Amplifier Mute Signal

2

2

2

--

Low level audio (+)

B1025*

1*

B1025*

--

Low level audio (-)

B1025*

1*

B1025*

--

Speaker Output (+)

1*

1*

1*

--

Speaker Output (-)

1*

1*

1*

--

Audio Amplifier Ground

--

2, 3

--

--

1. No or reduced sound from speaker.

2. Amplifier inoperative/no sound from speaker

3. Powered subwoofer inoperative

* Noticeable audio distortion possible

Circuit/System Description

Each of the audio output channel circuits (+) and (-), at the radio and audio amplifier have a DC bias voltage that is one half of the battery voltage. When using a DMM, each of the audio output channel circuits will measure approximately 6.5V DC. The audio being played on the system is produced by a varying AC voltage that is centered around the DC bias voltage on the same circuit. The AC voltage is what causes the speaker cone to move and produce sound. This voltage will vary depending on what type of audio is being listened to, talk or music, and type of music, as well as the volume setting of the system. Low volume and talk settings will measure around 1V AC and less, where constant music may measure 3V AC and slightly higher.

Diagnostic Aids
    • Improper speaker mounting or loose trim may cause an audible buzz or distortion. Inspect the appropriate speaker and the surrounding interior trim for proper and secure mounting. If the speaker or surrounding interior trim is found to be loose or improperly secured, correctly secure the item.
    • When equipped with an amplifier, it is possible for some individual circuit faults to affect more than one speakers operation. Perform diagnostic tests in the sequence listed to avoid misdiagnosis.

Reference Information

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

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

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

Radio ON, verify clear audio is heard from each audio speaker.

⇒If audio is inoperative from all speakers, refer to Amplifier Circuit Malfunction.
⇒If audio is inoperative from one or more, but not all speakers or the audio emitted from the speakers is not clear, refer to Speaker Circuit Malfunction.
⇒If the audio/bass is inoperative from one of the front door powered subwoofers, refer to Powered Subwoofer Circuit Malfunction.

Circuit/System Testing

Amplifier Circuit Malfunction U65

  1. Ignition OFF, disconnect the X1 harness connector at the audio amplifier.
  2. Ignition OFF, test for less than 10 Ω between the ground circuit terminal A and ground.
    3. ⇒If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Ignition ON, test for B+ between the B+ circuit terminal H and ground.
    4. ⇒If less than the specified value, test the B+ circuit for a short to ground or an open/high resistance.
  4. Ignition OFF, disconnect the X2 harness connector at the audio amplifier.
  5. Radio ON, test for 0.6-1.0 V between the amplifier mute signal circuit terminal B1 and ground.
    6. ⇒If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. 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.
  6. Radio ON, test for B+ between the antenna enable signal circuit terminal B11 and ground.
    7. ⇒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.
  7. If all circuits test normal, replace the audio amplifier.

Amplifier Circuit Malfunction U66

  1. Ignition OFF, disconnect the X1 harness connector at the audio amplifier.
  2. Ignition OFF, test for less than 10 Ω between the ground circuit terminal F and ground.
    3. ⇒If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Ignition ON, test for B+ between the B+ circuit terminal E and ground.
    4. ⇒If less than the specified value, test the B+ circuit for a short to ground or an open/high resistance.
  4. Ignition OFF, disconnect the X2 harness connector at the audio amplifier.
  5. Radio ON, test for 0.6-1.0 V between the amplifier mute signal circuit terminal A8 and ground.
    6. ⇒If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. 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.
  6. Radio ON, test for B+ between the antenna enable signal circuit terminal A3 and ground.
    7. ⇒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.
  7. If all circuits test normal, replace the audio amplifier.

Speaker Circuit Malfunction -- Radio Output Testing -- U65

  1. Ignition OFF, disconnect the X2 harness connector at the audio amplifier.
  2. Radio ON, test for 5.0-7.5 V between the appropriate signal circuit terminal listed below and ground.
    3. • Left front low level audio signal (+) terminal B10
    • Left front low level audio signal (-) terminal B9
    • Right front low level audio signal (+) terminal B8
    • Right front low level audio signal (-) terminal B7
    • Left rear low level audio signal (+) terminal B6
    • Left rear low level audio signal (-) terminal B5
    • Right rear low level audio signal (+) terminal B4
    • Right rear low level audio signal (-) terminal B3
    ⇒If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. 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.
  3. If all circuits test normal, replace the amplifier.

Speaker Circuit Malfunction -- Radio Output Testing -- U66

  1. Ignition OFF, disconnect the X2 harness connector at the audio amplifier.
  2. Radio ON, test for 5.0-7.5 V between the appropriate signal circuit terminal listed below and ground.
    3. • Left front low level audio signal (+) terminal A7
    • Left front low level audio signal (-) terminal A6
    • Right front low level audio signal (+) terminal B6
    • Right front low level audio signal (-) terminal B7
    • Left rear low level audio signal (+) terminal A4
    • Left rear low level audio signal (-) terminal A5
    • Right rear low level audio signal (+) terminal B5
    • Right rear low level audio signal (-) terminal B4
    ⇒If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. 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.
  3. If all circuits test normal, replace the amplifier.

Speaker Circuit Malfunction -- Amplifier Output Testing -- U65

  1. Ignition OFF, disconnect the X1 and X2 connectors at the amplifier.
  2. Radio ON, test for less than 1 V between the appropriate signal circuit terminal listed below and ground:
    3. • Left front midrange speaker output (+) - terminal A9 X2
    • Left front midrange speaker output (-) - terminal A10 X2
    • Right front midrange speaker output (+) - terminal A11 X2
    • Right front midrange speaker output (-) - terminal A12 X2
    • Rear speaker output (+) - terminal A7 X2
    • Rear speaker output (-) - terminal A8 X2
    • Front center speaker output (+) - terminal A5 X2
    • Front center speaker output (-) - terminal A6 X2
    • Left front subwoofer speaker output (+) - terminal B X1
    • Left front subwoofer speaker output (-) - terminal G X1
    • Right front subwoofer speaker output (+) - terminal C X1
    • Right front subwoofer speaker output (-) - terminal F X1
    ⇒If greater than the specified range, test both circuits of the affected speaker for a short to voltage.
  3. Radio OFF, test for infinite resistance between the appropriate signal circuit terminal listed below and ground:
    4. • Left front midrange speaker output (+) - terminal A9 X2
    • Left front midrange speaker output (-) - terminal A10 X2
    • Right front midrange speaker output (+) - terminal A11 X2
    • Right front midrange speaker output (-) - terminal A12 X2
    • Rear speaker output (+) - terminal A7 X2
    • Rear speaker output (-) - terminal A8 X2
    • Front center speaker output (+) - terminal A5 X2
    • Front center speaker output (-) - terminal A6 X2
    • Left front subwoofer speaker output (+) - terminal B X1
    • Left front subwoofer speaker output (-) - terminal G X1
    • Right front subwoofer speaker output (+) - terminal C X1
    • Right front subwoofer speaker output (-) - terminal F X1
    ⇒If less than the specified value, test both circuits of the affected speaker for a short to ground.
  4. If all circuits test normal, reconnect all harness connectors at the amplifier.
  5. Radio ON, disconnect the appropriate speaker.
  6. Test for 5.0-7.5 V between the signal circuit terminal A and ground.
    7. ⇒If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the radio.
    ⇒If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the radio.
  7. Test for 5.0-7.5 V between the signal circuit terminal B and ground.
    8. ⇒If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the radio.
    ⇒If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the radio.
  8. If all circuits test normal, replace the speaker.

Speaker Circuit Malfunction -- Amplifier Output Testing -- U66

  1. Ignition OFF, disconnect the X1 and X2 connectors at the amplifier.
  2. Radio ON, test for less than 1 V between the appropriate signal circuit terminal listed below and ground:
    3. • Left front midrange speaker output (+) - terminal B9 X2
    • Left front midrange speaker output (-) - terminal B10 X2
    • Right front midrange speaker output (+) - terminal B11 X2
    • Right front midrange speaker output (-) - terminal B12 X2
    • Left rear midrange speaker output (+) - terminal A11 X2
    • Left rear midrange speaker output (-) - terminal A12 X2
    • Right rear midrange speaker output (+) - terminal A9 X2
    • Right rear midrange speaker output (-) - terminal A10 X2
    • Front center speaker output (+) - terminal G X1
    • Front center speaker output (-) - terminal H X1
    • Left front subwoofer speaker output (+) - terminal D X1
    • Left front subwoofer speaker output (-) - terminal C X1
    • Right front subwoofer speaker output (+) - terminal C X1
    • Right front subwoofer speaker output (-) - terminal F X1
    ⇒If greater than the specified range, test both circuits of the affected speaker for a short to voltage.
  3. Radio OFF, test for infinite resistance between the appropriate signal circuit terminal listed below and ground:
    4. • Left front midrange speaker output (+) - terminal B9 X2
    • Left front midrange speaker output (-) - terminal B10 X2
    • Right front midrange speaker output (+) - terminal B11 X2
    • Right front midrange speaker output (-) - terminal B12 X2
    • Left rear midrange speaker output (+) - terminal A11 X2
    • Left rear midrange speaker output (-) - terminal A12 X2
    • Right rear midrange speaker output (+) - terminal A9 X2
    • Right rear midrange speaker output (-) - terminal A10 X2
    • Front center speaker output (+) - terminal G X1
    • Front center speaker output (-) - terminal H X1
    • Left front subwoofer speaker output (+) - terminal D X1
    • Left front subwoofer speaker output (-) - terminal C X1
    • Right front subwoofer speaker output (+) - terminal C X1
    • Right front subwoofer speaker output (-) - terminal F X1
    ⇒If less than the specified value, test both circuits of the affected speaker for a short to ground.
  4. If all circuits test normal, reconnect all harness connectors at the amplifier.
  5. Radio ON, disconnect the appropriate speaker.
  6. Test for 5.0-7.5 V between the signal circuit terminal A and ground.
    7. ⇒If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the radio.
    ⇒If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the radio.
  7. Test for 5.0-7.5 V between the signal circuit terminal B and ground.
    8. ⇒If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the radio.
    ⇒If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the radio.
  8. If all circuits test normal, replace the speaker.

Powered Subwoofer Circuit Malfunction

  1. Disconnect the harness connector at the inoperative subwoofer.
  2. Ignition OFF, test for less than 10 Ω between the ground circuit terminal 4 and ground
    3. ⇒If greater than specified range, test the ground circuit for an open/high resistance.
  3. Ignition ON, test for B+ between circuit terminal 5 and ground.
    4. ⇒If less then the specified value, test the B+ circuit for a short to ground or an open/high resistance.
  4. Radio ON, test for B+ between the antenna enable signal circuit terminal 3 and ground.
    5. ⇒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. Radio ON, test for 5.0-7.5 V between the signal circuit terminal 2 and ground.
    6. ⇒If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the audio amplifier.
    ⇒If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the audio amplifier.
  6. Test for 5.0-7.5 V between the signal circuit terminal 1 and ground.
    7. ⇒If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the audio amplifier.
    ⇒If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the audio amplifier.
  7. If all circuits test normal, replace the appropriate subwoofer.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Speaker Replacement Reference
    •  Control Module References for Audio Amplifier and Radio replacement, setup, and programming