GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2007 🢒 Sierra Denali 🢒 Driver Information and Entertainment 🢒 Cellular, Entertainment, and Navigation 🢒 DTC B1025-B1095

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.

DTC Descriptors

DTC B1025 01: Audio Output 1 Left Front Circuit Short to Battery

DTC B1025 02: Audio Output 1 Left Front Circuit Short to Ground

DTC B1035 01: Audio Output 2 Right Front Circuit Short to Battery

DTC B1035 02: Audio Output 2 Right Front Circuit Short to Ground

DTC B1045 01:  Audio Output 3 Left Rear Circuit Short to Battery

DTC B1045 02:  Audio Output 3 Left Rear Circuit Short to Ground

DTC B1055 01:  Audio Output 4 Right Rear Circuit Short to Battery

DTC B1055 02:  Audio Output 4 Right Rear Circuit Short to Ground

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

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

B1025 02, *

1

B1025 01, *

--

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

B1025 02, *

1

B1025 01, *

--

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

B1035 02, *

1

B1035 01, *

--

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

B1035 02, *

1

B1035 01, *

--

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

B1045 02, *

1

B1045 01, *

--

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

B1045 02, *

1

B1045 01, *

--

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

B1055 02, *

1

B1055 01, *

--

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

B1055 02, *

1

B1055 01, *

--

1. No or reduced audio

* 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

Set by Radio

The radio sets a current status for this DTC when a short to ground, short to voltage or an open is detected on any of the 4 speaker channel outputs from the radio.

Set by Bose Amplifier

The DTC will not set during normal amplifier operation. The vehicle must have the ignition OFF for several hours and the fault must be present during amplifier power-up.

DTC B1025 01, B1035 01, B1045 01, B1055 01

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

DTC B1025 02, B1035 02, B1045 02, B1055 02

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 condition responsible for setting the DTC no longer exists.
    • A history DTC will clear once 100 consecutive malfunction-free ignition cycles have occurred.

Diagnostic Aids

Speakers located in the front A-pillar are connected to the same channel as the speaker in the door. A DTC will only set after the amplifier only on up-level radios.

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

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

Important: This DTC can be set by either the radio or the amplifier. If the DTC was set by the radio, diagnose the appropriate audio output circuits to the speakers or the low level inputs to the amplifier (if equipped). If the DTC was set by the amplifier, diagnose audio output signals to the speakers from the amplifier. If equipped with rear seat audio (RSA) (U42), the RSA must be turned off to perform proper speaker 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 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. Test for 5.0-7.5 volts between the signal circuit terminal B and ground.
    4. ⇒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.
  4. If all circuits test normal, replace the speaker.

DTC Set By The Radio (-Y91) (-U42)

  1. Ignition OFF, disconnect the C3 harness 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 level audio signal (+) - terminal 15 C3
    • Left front low level audio signal (-) - terminal 7 C3
    • Right front low level audio signal (+) - terminal 14 C3
    • Right front low level audio signal (-) - terminal 6 C3
    • Left rear low level audio signal (+) - terminal 13 C3
    • Left rear low level audio signal (-) - terminal 5 C3
    • Right rear low level audio signal (+) - terminal 12 C3
    • Right rear low level audio signal (-) - terminal 4 C3
    ⇒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.

DTC Set By Radio (-Y91) (+U42)

  1. Ignition OFF, disconnect the C3 harness 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 level audio signal (+) - terminal 15
    • Left front low level audio signal (-) - terminal 7
    • Right front low level audio signal (+) - terminal 14
    • Right front low level audio signal (-) - terminal 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.
  3. Ignition OFF, reconnect the C3 harness connector at the amplifier.
  4. Disconnect the C2 harness connector at the rear seat audio (RSA) module.
  5. Radio ON, test for 5.0-7.5 volts between the appropriate signal circuit terminal listed below and ground.
    6. • Left rear low level audio signal (+) - terminal 1
    • Left rear low level audio signal (-) - terminal 2
    • Right rear low level audio signal (+) - terminal 3
    • Right rear low level audio signal (-) - terminal 4
    ⇒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 rear seat audio (RSA) module.
    ⇒If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the rear seat audio (RSA) module.
  6. Ignition OFF, reconnect the C2 harness connector at the rear seat audio (RSA) module.
  7. Disconnect the C3 harness connector at the amplifier.
  8. Radio ON, test for 5.0-7.5 volts between the appropriate signal circuit terminal listed below and ground.
    9. • Left rear low level audio signal (+) - terminal 13 C3
    • Left rear low level audio signal (-) - terminal 5 C3
    • Right rear low level audio signal (+) - terminal 12 C3
    • Right rear low level audio signal (-) - terminal 4 C3
    ⇒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 rear seat audio (RSA) module.
    ⇒If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the rear seat audio (RSA) module.
  9. If all circuits test normal, replace the amplifier.

DTC Set By The Radio (+Y91) (-U42)

  1. Ignition OFF, disconnect the C1 and C3 harness connectors 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 level audio signal (+) - terminal 11 C3
    • Left front low level audio signal (-) - terminal 12 C3
    • Right front low level audio signal (+) - terminal 3 C3
    • Right front low level audio signal (-) - terminal 4 C3
    • Left rear low level audio signal (+) - terminal 15 C2
    • Left rear low level audio signal (-) - terminal 14 C2
    • Right rear low level audio signal (+) - terminal 16 C2
    • Right rear low level audio signal (-) - terminal 8 C2
    ⇒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.

DTC Set By Radio (+Y91) (+U42)

  1. Ignition OFF, disconnect the C3 harness 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 level audio signal (+) - terminal 11 C3
    • Left front low level audio signal (-) - terminal 12 C3
    • Right front low level audio signal (+) - terminal 3 C3
    • Right front low level audio signal (-) - terminal 4 C3
    ⇒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. Ignition OFF, reconnect the C3 harness connector at the amplifier.
  4. Disconnect the C2 harness connector at the rear seat audio (RSA) module.
  5. Radio ON, test for 5.0-7.5 volts between the appropriate signal circuit terminal listed below and ground.
    6. • Left rear low level audio signal (+) - terminal 1
    • Left rear low level audio signal (-) - terminal 2
    • Right rear low level audio signal (+) - terminal 3
    • Right rear low level audio signal (-) - terminal 4
    ⇒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 rear seat audio (RSA) module.
    ⇒If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the rear seat audio (RSA) module.
  6. Ignition OFF, reconnect the C2 harness connector at the rear seat audio (RSA) module.
  7. Disconnect the C2 harness connector at the amplifier.
  8. Radio ON, test for 5.0-7.5 volts between the appropriate signal circuit terminal listed below and ground.
    9. • Left rear low level audio signal (+) - terminal 15 C2
    • Left rear low level audio signal (-) - terminal 14 C2
    • Right rear low level audio signal (+) - terminal 16 C2
    • Right rear low level audio signal (-) - terminal 8 C2
    ⇒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 rear seat audio (RSA) module.
    ⇒If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the rear seat audio (RSA) module.
  9. If all circuits test normal, replace the amplifier.

DTC Set by Audio Amplifier (-Y91)

  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 speaker output (+) - terminal 4 C2
    • Left front speaker output (-) - terminal 3 C2
    • Right front speaker output (+) - terminal 2 C2
    • Right front low speaker output (-) - terminal 1 C2
    • Left rear speaker output (+) - terminal 8 C2
    • Left rear speaker output (-) - terminal 7 C2
    • Right rear speaker output (+) - terminal 6 C2
    • Right rear speaker output (-) - terminal 5 C2
    • Left subwoofer speaker output (+) - terminal 7 C1
    • Left subwoofer speaker output (-) - terminal 3 C1
    • Right subwoofer speaker output (+) - terminal 6 C1
    • Right subwoofer speaker output (-) - terminal 2 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 speaker output (+) - terminal 4 C2
    • Left front speaker output (-) - terminal 3 C2
    • Right front speaker output (+) - terminal 2 C2
    • Right front low speaker output (-) - terminal 1 C2
    • Left rear speaker output (+) - terminal 8 C2
    • Left rear speaker output (-) - terminal 7 C2
    • Right rear speaker output (+) - terminal 6 C2
    • Right rear speaker output (-) - terminal 5 C2
    • Left subwoofer speaker output (+) - terminal 7 C1
    • Left subwoofer speaker output (-) - terminal 3 C1
    • Right subwoofer speaker output (+) - terminal 6 C1
    • Right subwoofer speaker output (-) - terminal 2 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.
  7. If the circuit tests normal, replace the appropriate speaker.

DTC Set by Audio Amplifier (+Y91)

  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 speaker output (+) - terminal 4 C2
    • Left front speaker output (-) - terminal 5 C2
    • Right front speaker output (+) - terminal 7 C2
    • Right front low speaker output (-) - terminal 6 C2
    • Left rear speaker output (+) - terminal 8 C2
    • Left rear speaker output (-) - terminal 7 C2
    • Right rear speaker output (+) - terminal 16 C2
    • Right rear speaker output (-) - terminal 8 C2
    • Front center speaker output (+) - terminal 13 C2
    • Front center speaker output (-) - terminal 12 C2
    • Left subwoofer speaker output (+) - terminal 1 C1
    • Left subwoofer speaker output (-) - terminal 2 C1
    • Right subwoofer speaker output (+) - terminal 7 C1
    • Right subwoofer speaker output (-) - terminal 3 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 speaker output (+) - terminal 4 C2
    • Left front speaker output (-) - terminal 5 C2
    • Right front speaker output (+) - terminal 7 C2
    • Right front low speaker output (-) - terminal 6 C2
    • Left rear speaker output (+) - terminal 8 C2
    • Left rear speaker output (-) - terminal 7 C2
    • Right rear speaker output (+) - terminal 16 C2
    • Right rear speaker output (-) - terminal 8 C2
    • Front center speaker output (+) - terminal 13 C2
    • Front center speaker output (-) - terminal 12 C2
    • Left subwoofer speaker output (+) - terminal 1 C1
    • Left subwoofer speaker output (-) - terminal 2 C1
    • Right subwoofer speaker output (+) - terminal 7 C1
    • Right subwoofer speaker output (-) - terminal 3 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.
  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 and Radio replacement, setup, and programming