GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Isuzu 🢒 2009 🢒 Ascender - 2WD 🢒 DTC 🢒 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 provides 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

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 (+)

B1035*

1

B1035*

--

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

B1035*

1

B1035*

--

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

B1045*

1

B1045*

--

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

B1045*

1

B1045*

--

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

B1055*

1

B1055*

--

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

B1055*

1

B1055*

--

1. 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 at the 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 6.5V 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 short to ground is detected on the specified (+) or (-) signal circuit.

Action Taken When the DTC Sets

The radio disables audio output on the appropriate channel.

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

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, 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

Note: If equipped with rear seat audio (RSA), the RSA must be turned off to perform proper speaker testing.

Without Amplifier or RSA

  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.
  3. Test for 5.0-7.5 volts between the signal circuit terminal B and ground.
    4. ⇒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, test or replace the speaker.

Without Amplifier with RSA -- Front Speaker Testing

  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.
  3. Test for 5.0-7.5 volts between the signal circuit terminal B and ground.
    4. ⇒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 speaker.

Without Amplifier with RSA -- Rear Speaker Testing

  1. Ignition OFF, disconnect the CJ2 harness connector at the HVAC Control Module.
  2. Radio ON, test for 5.0-7.5 volts between the appropriate signal circuit terminal listed below and ground.
    3. • Left rear low level audio signal (+) - terminal B3
    • Left rear low level audio signal (-) - terminal B7
    • Right rear low level audio signal (+) - terminal B4
    • Right rear low level audio signal (-) - terminal B8
    ⇒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.
  3. Ignition OFF, disconnect the harness connector at the appropriate speaker.
  4. Radio ON, test for 5.0-7.5 volts between the signal circuit terminal A 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 HVAC Control Module.
    ⇒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 HVAC Control Module.
  5. Test for 5.0-7.5 volts between the signal circuit terminal B and ground.
    6. ⇒If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the HVAC Control Module.
    ⇒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 HVAC Control Module.
  6. If all circuits test normal, replace the speaker.

With Amplifier - Front and Rear Speaker Testing

  1. Ignition OFF, disconnect the X1 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 B10 X1
    • Left front low level audio signal (-) terminal B9 X1
    • Right front low level audio signal (+) - terminal B8 X1
    • Right front low level audio signal (-) - terminal B7 X1
    • Left rear low level audio signal (+) - terminal B6 X1
    • Left rear low level audio signal (-) - terminal B5X1
    • Right rear low level audio signal (+) - terminal B4 X1
    • Right rear low level audio signal (-) - terminal B3 X1
    ⇒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.
  3. If all circuits test normal, replace the amplifier.

With Amplifier and RSA - Front and Rear Speaker Testing

  1. Ignition OFF, disconnect the X1 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 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 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.
  3. Ignition OFF, reconnect the X1 harness connector at the amplifier.
  4. Disconnect the CJ2 harness connector at the HVAC Control 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 B3
    • Left rear low level audio signal (-) - terminal B7
    • Right rear low level audio signal (+) - terminal B4
    • Right rear low level audio signal (-) - terminal B8
    ⇒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. Ignition OFF, reconnect the CJ2 harness connector at the HVAC Control Module.
  7. Disconnect the X1 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 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 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.
    ⇒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.
  9. 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 Radio, Amplifier, and HVAC Control Module replacement, setup, and programming