GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2007 🢒 TopKick C-Series (Conventional) C4/C5 🢒 Safety and Security 🢒 Supplemental Inflatable Restraints 🢒 DTC B1025, B1035, B1045, or B1055

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 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

Amplifier B+

2

2

--

--

Antenna Enable Signal

2

2

--

--

Speaker Output Circuit (+)

B10XX 02*,**

1

B10XX 01*,**

--

Speaker Output Circuit (-)

B10XX 02*,**

1

B10XX 01*,**

--

Amplifier Ground

--

2

--

--

1. No or reduced sound from speaker

2. Amplifier inoperative/no sound from speakers

* Sets associated speaker DTC with appropriate symptom type

** Noticeable audio distortion possible

Circuit/System Description

Each of the audio output channel circuits (+) and (-), at the radio and audio amplifier (if equipped) 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 6.5 V 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 3 V AC and slightly higher.

Conditions for Running the DTC
    • Radio ON.
    • Battery voltage must be between 9-16 V.

Conditions for Setting the DTC

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.

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 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 1 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 2 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 appropriate speaker.

With Amplifier

  1. Ignition OFF, disconnect the C3 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 12
    • Left front low level audio signal (-) - terminal 10
    • Right front low level audio signal (+) - terminal 9
    • Right front low level audio signal (-) - terminal 11
    • Left rear low level audio signal (+) - terminal 3
    • Left rear low level audio signal (-) - terminal 1
    • Right rear low level audio signal (+) - terminal 4
    • Right rear low level audio signal (-) - terminal 2
    ⇒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.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Speaker Replacement Reference
    •  Control Module Referencesfor Amplifier and Radio replacement, setup, and programming