GM Service Manual Online
For 1990-2009 cars only

DTC B1025, B1035, B1045, or B1055 Navigation Radio Only

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 provide an overview of each diagnostic category.

DTC Descriptors

DTC B1025: Audio Output 1 Left Front Circuit

DTC B1035: Audio Output 2 Right Front Circuit

DTC B1045:  Audio Output 3 Left Rear Circuit

DTC B1055:  Audio Output 4 Right Rear Circuit

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Amplifier B+

--

1

--

--

Radio ON/ Amp Turn ON Signal

1

1

--

--

Left Front Speaker Output (+)/Left Front Low Level Audio Signal (+)

B1025, *

2

B1025, *

--

Left Front Speaker Output (-)/Left Front Low Level Audio Signal (-)

B1025, *

2

B1025, *

--

Right Front Speaker Output (+)/Right Front Low Level Audio Signal (+)

B1035, *

2

B1035, *

--

Right Front Speaker Output (-)/Right Front Low Level Audio Signal (-)

B1035, *

2

B1035, *

--

Left Rear Speaker Output (+)/Left Rear Low Level Audio Signal (+)

B1045, *

2

B1045, *

--

Left Rear Speaker Output (-)/Left Rear Low Level Audio Signal (-)

B1045, *

2

B1045, *

--

Right Rear Speaker Output (+)/Right Rear Low Level Audio Signal (+)

B1055,*

2

B1055,*

--

Right Rear Speaker Output (-)/Right Rear Low Level Audio Signal (-)

B1055,*

2

B1055,*

--

Amplifier Ground

--

1

--

--

1. Amplifier inoperative/no sound from speakers

2. No or reduced sound from speaker

* 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.

Conditions for Running the DTC

The radio is ON.

Conditions for Setting the DTC

The radio sets a current status for this DTC when a short to ground or short to voltage is detected on any of the speaker channel outputs from the radio.

B1025, B1035, B1045, B1055

A short to voltage or a short to ground is detected on the specified (+) or (-) signal circuit

Action Taken When the DTC Sets

No sound is present from one or more of the speakers.

Conditions for Clearing the DTC

The fault condition becomes history if not present for 0.25 seconds.

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

Radio ON, adjust the fade and balance controls on the radio to test all four channels individually. Each of the four channels should produce clear and even sound.

Circuit/System Testing

Without Amplifier

  1. Ignition OFF, disconnect the harness connector at the appropriate speaker.
  2. Radio ON, test for 5.0-7.5 volts between the signal circuit terminal A and ground.
  3. 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.
  4. Test for 5.0-7.5 volts between the signal circuit terminal B and ground.
  5. 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.
  6. If all circuits test normal, replace the speaker.

With Amplifier

  1. Ignition OFF, disconnect the X1 connector at the amplifier.
  2. Radio ON, test for 5.0-7.5 volts between the appropriate signal circuit terminal listed below and ground.
  3. • Left front low audio signal (+) - terminal 1
    • Left front low audio signal (-) - terminal 2
    • Right front low audio signal (+) - terminal 10
    • Right front low audio signal (-) - terminal 9
    • Left rear low audio signal (+) - terminal 4
    • Left rear low audio signal (-) - terminal 3
    • Right rear low audio signal (+) - terminal 11
    • Right rear low audio signal (-) - terminal 12
    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.
  4. If all circuits test normal, replace the amplifier.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

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

DTC B1025, B1035, B1045, or B1055 Non-Navigation Radio

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 provide an overview of each diagnostic category.

DTC Descriptors

DTC B1025: Speaker Output Shorted to Ground or Voltage

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Amplifier B+

--

2

--

--

Radio ON/ Amp Turn ON Signal

2

2

--

--

Left Front Speaker Output (+)/Left Front Low Level Audio Signal (+)

B1025*

1

B1025*

--

Left Front Speaker Output (-)/Left Front Low Level Audio Signal (-)

B1025*

1

B1025*

--

Right Front Speaker Output (+)/Right Front Low Level Audio Signal (+)

B1025*

1

B1025*

--

Right Front Speaker Output (-)/Right Front Low Level Audio Signal (-)

B1025*

1

B1025*

--

Left Rear Speaker Output (+)/Left Rear Low Level Audio Signal (+)

B1025*

1

B1025*

--

Left Rear Speaker Output (-)/Left Rear Low Level Audio Signal (-)

B1025*

1

B1025*

--

Right Rear Speaker Output (+)/Right Rear Low Level Audio Signal (+)

B1025*

1

B1025*

--

Right Rear Speaker Output (-)/Right Rear Low Level Audio Signal (-)

B1025*

1

B1025*

--

Amplifier Ground

--

2

--

--

1. No or reduced sound from speaker

2. Amplifier inoperative/no sound from speakers

* Noticeable Distorted Audio 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.

Conditions for Running the DTC

The radio is ON.

Conditions for Setting the DTC

A short to voltage or a short to ground is detected on a speaker output signal circuit.

Action Taken When the DTC Sets

The radio disables its outputs on one or more channels, producing no sound.

Conditions for Clearing the DTC

    •  A current DTC will clear when the conditions for setting are no longer seen.
    • A history DTC will clear after 100 malfunction free ignition cycles.

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

Radio ON, adjust the fade and balance controls on the radio to test all four channels individually. Each of the four channels should produce clear and even sound.

Circuit/System Testing

Without Amplifier

  1. Ignition OFF, disconnect the harness connector at the appropriate speaker.
  2. Radio ON, test for 5.0-7.5 volts between the signal circuit terminal A and ground.
  3. 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.
  4. Test for 5.0-7.5 volts between the signal circuit terminal B and ground.
  5. 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.
  6. If all circuits test normal, replace the speaker.

With Amplifier

  1. Ignition OFF, disconnect the X1 connector at the amplifier.
  2. Radio ON, test for 5.0-7.5 volts between the appropriate signal circuit terminal listed below and ground.
  3. • Left front low audio signal (+) - terminal 1
    • Left front low audio signal (-) - terminal 2
    • Right front low audio signal (+) - terminal 10
    • Right front low audio signal (-) - terminal 9
    • Left rear low audio signal (+) - terminal 4
    • Left rear low audio signal (-) - terminal 3
    • Right rear low audio signal (+) - terminal 11
    • Right rear low audio signal (-) - terminal 12
    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.
  4. If all circuits test normal, replace the amplifier.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

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