GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2007 🢒 CTS 🢒 Diagnostic Navigation 🢒 Vehicle Diagnostic Information 🢒 Speakers Inoperative - One or More

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

Amplifier B+

--

1

--

--

Speaker Output Circuit (+)

2

2

2

--

Speaker Output Circuit (-)

2

2

2

--

Subwoofer Signal (+)

3

3

3

--

Subwoofer Signal (-)

3

3

3

--

Amplifier Ground

--

1

--

--

1. Amplifier inoperative/no sound from all speakers

2. No or reduced sound from speaker

3. No or reduced sound from subwoofer

Circuit/System Description

Each of the audio output channel circuits (+) and (-) have a varying AC mV signal that is produced by the radio and sent to the amplifier. The amplifier then processes these signals and passes the audio along with a DC bias voltage to the appropriate speakers. The audio being played on the system is produced by the varying AC voltage. 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. When using a DMM, each of the audio amplifier output channel circuits will measure approximately 6.5V DC.

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

Entertainment/Communication 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 the appropriate Speaker Circuit Malfunction.

Circuit/System Testing

Amplifier Circuit Malfunction RPO U57

  1. Ignition OFF, disconnect the C1 harness connector at the audio amplifier.
  2. Test for less than 10 ohms 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 then specified value, test the circuit for a short to ground, or an open/high resistance.
  4. If all circuits test normal, replace the audio amplifier.

Amplifier Circuit Malfunction RPO U66

  1. Ignition OFF, disconnect the C1 harness connector at the audio amplifier.
  2. Test for less than 10 ohms 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 B and ground.
    4. ⇒If less then specified value, test the circuit for a short to ground, or an open/high resistance.
  4. If all circuits test normal, replace the audio amplifier.

Speaker Malfunction Radio Output Testing RPO U57

  1. Ignition OFF, disconnect the C2 connector at the amplifier.
  2. Radio ON, test for a varying mV AC voltage reading between the appropriate signal circuit terminals listed below and ground.
    3. • Left low level audio signal (+) - terminal B10
    • Left low level audio signal (-) - terminal B9
    • Right low level audio signal (+) - terminal B11
    • Right low level audio signal (-) - terminal B8
    ⇒If the varrying Mv A/C voltage reading is not present, test the signal circuit for a short to voltage, short to ground, or an open/high resistance. If the circuit tests normal, replace the radio.
  3. If all circuits test normal, replace the amplifier.

Speaker Malfunction Radio Output Testing RPO U66

  1. Ignition OFF, disconnect the C3 connector at the amplifier.
  2. Radio ON, test for a varying mV AC voltage reading between the appropriate signal circuit terminals listed below and ground.
    3. • Left low level audio signal (+) - terminal B7
    • Left low level audio signal (-) - terminal B6
    • Right low level audio signal (+) - terminal B5
    • Right low level audio signal (-) - terminal B4
    ⇒If the varrying Mv A/C voltage reading is not present, test the signal circuit for a short to voltage, short to ground, or an open/high resistance. If the circuit tests normal, replace the radio.
  3. If all circuits test normal, replace the amplifier.

Speaker Malfunction Amplifier Output Testing RPO U57

  1. Ignition OFF, disconnect the C1 and C2 connectors at the amplifier.
  2. Radio ON, test for less than 1 volt between the appropriate signal circuit terminal listed below and ground:
    3. • Left front tweeter speaker output (+) - terminal A4 C2
    • Left front tweeter speaker output (-) - terminal A5 C2
    • Right front tweeter speaker output (+) - terminal A9 C2
    • Right front tweeter speaker output (-) - terminal A8 C2
    • Left rear midrange speaker output (+) - terminal A3 C2
    • Left rear midrange speaker output (-) - terminal A2 C2
    • Right rear midrange speaker output (+) - terminal A10 C2
    • Right rear midrange speaker output (-) - terminal A11 C2
    • Front center speaker output (+) - terminal A7 C2
    • Front center speaker output (-) - terminal A6 C2
    • Rear subwoofer speaker output (+) - terminal B C1
    • Rear subwoofer speaker output (-) - terminal G C1
    ⇒If greater than the specified range, test both circuits of the affected speaker for a short to voltage.
  3. Radio ON, test for infinite resistance between the appropriate signal circuit terminal listed below and ground:
    4. • Left front tweeter speaker output (+) - terminal A4 C2
    • Left front tweeter speaker output (-) - terminal A5 C2
    • Right front tweeter speaker output (+) - terminal A9 C2
    • Right front tweeter speaker output (-) - terminal A8 C2
    • Left rear midrange speaker output (+) - terminal A3 C2
    • Left rear midrange speaker output (-) - terminal A2 C2
    • Right rear midrange speaker output (+) - terminal A10 C2
    • Right rear midrange speaker output (-) - terminal A11 C2
    • Front center speaker output (+) - terminal A7 C2
    • Front center speaker output (-) - terminal A6 C2
    • Rear subwoofer speaker output (+) - terminal B C1
    • Rear subwoofer speaker output (-) - terminal G C1
    ⇒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. Ignition ON, radio ON, disconnect the appropriate speaker.
  6. Test for 5.0-7.5 volts between the signal circuit terminals and ground.
    7. ⇒If less then the specified range, test the circuit for an open/high resistance. If the circuit tests normal, replace the amplifier.
    ⇒If greater then the specified range, test the circuit for a short to voltage. If the circuit tests normal, replace the amplifier.
  7. If the circuit tests normal, replace the appropriate speaker.

Speaker Malfunction Amplifier Output Testing RPO Code U66

  1. Ignition OFF, disconnect the C2 and C3 connectors at the amplifier.
  2. Radio ON, test for less than 1 volt between the appropriate signal circuit terminal listed below and ground:
    3. • Left front tweeter speaker output (+) - terminal A3 C3
    • Left front tweeter speaker output (-) - terminal A4 C3
    • Right front tweeter speaker output (+) - terminal A2 C3
    • Right front tweeter speaker output (-) - terminal A1 C3
    • Left front midrange speaker output (+) - terminal A5 C3
    • Left front midrange speaker output (-) - terminal A6 C3
    • Right front midrange speaker output (+) - terminal A4 C2
    • Right front midrange speaker output (-) - terminal A3 C2
    • Left rear midrange speaker output (+) - terminal A8 C2
    • Left rear midrange speaker output (-) - terminal A7 C2
    • Right rear midrange speaker output (+) - terminal A6 C2
    • Right rear midrange speaker output (-) - terminal A5 C2
    • Rear subwoofer speaker coil 1 output (+) - terminal A7 C2
    • Rear subwoofer speaker coil 1 output (-) - terminal A8 C2
    • Rear subwoofer speaker coil 2 output (+) - terminal A9 C2
    • Rear subwoofer speaker coil 2 output (-) - terminal A10 C2
    ⇒If greater than the specified range, test both circuits of the affected speaker for a short to voltage.
  3. Radio ON, test for infinite resistance between the appropriate signal circuit terminal listed below and ground:
    4. • Left front tweeter speaker output (+) - terminal A3 C3
    • Left front tweeter speaker output (-) - terminal A4 C3
    • Right front tweeter speaker output (+) - terminal A2 C3
    • Right front tweeter speaker output (-) - terminal A1 C3
    • Left front midrange speaker output (+) - terminal A5 C3
    • Left front midrange speaker output (-) - terminal A6 C3
    • Right front midrange speaker output (+) - terminal A4 C2
    • Right front midrange speaker output (-) - terminal A3 C2
    • Left rear midrange speaker output (+) - terminal A8 C2
    • Left rear midrange speaker output (-) - terminal A7 C2
    • Right rear midrange speaker output (+) - terminal A6 C2
    • Right rear midrange speaker output (-) - terminal A5 C2
    • Rear subwoofer speaker coil 1 output (+) - terminal A7 C2
    • Rear subwoofer speaker coil 1 output (-) - terminal A8 C2
    • Rear subwoofer speaker coil 2 output (+) - terminal A9 C2
    • Rear subwoofer speaker coil 2 output (-) - terminal A10 C2
    ⇒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. Ignition OFF, disconnect the appropriate speaker.
  6. Radio ON, test for 5.0-7.5 volts between the signal circuit terminals and ground.
    7. ⇒If less then the specified range test the circuit for an open/high resistance. If the circuit tests normal, replace the amplifier.
    ⇒If greater then the specified range, test the circuit for a short to voltage. If the circuit tests normal, replace the amplifier.
  7. If the circuit tests normal, replace the appropriate speaker.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Speaker Replacement Reference
    •  Control Module References for amplifier or radio replacement