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DTC B1287

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 B1287 01: Amplifier Control Signal Circuit Short to Battery

DTC B1287 02: Amplifier Control Signal Circuit Short to Ground

DTC B1287 04: Amplifier Control Signal Circuit Open

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Amplifier Control

DTC B1287 02,**

DTC B1287 04,**

DTC B1287 01,*

-

* No audio output.

** 4 Channel unmute, possible noise in speakers when radio muted or turned off

Circuit/System Description

The radio amplifier control circuit provides varying pulse width modulated (PWM) signals to control overall muting of the amplifier. The PWM signals are varying duty cycle percentages ranging from 0-100%. A low duty cycle unmutes all amplifier channels and a high duty cycle mutes all amplifier channels. The radio monitors the amplifier control circuit for faults. When a fault is detected the radio sets the appropriate DTC.

Conditions for Running the DTC

The following are conditions that must be present in order for the radio to enable the diagnostics.

    • The radio is in ACCESSORY, RUN, or Retained Accessory power mode.
    • The system voltage is at least 9 V and no more than 16 V.

Conditions for Setting the DTC

The radio detects a fault on the Amplifier Control circuit 400 ms after radio activates the Remote Enable circuit.

Action Taken When the DTC Sets

Radio sets the DTC and continues to output correct state.

Conditions for Clearing the DTC
    • The condition must be corrected.
    • A history DTC clears after 100 malfunction-free ignition cycles.
    • The radio receives the clear code command from the scan tool.

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

Verify the audio system performance by adjusting the fade and balance of the speaker outputs.

Circuit/System Testing

RPO Code UQA

  1. Ignition OFF, disconnect the X1 harness connector at the A11 Radio.
  2. Ignition ON, test for less than 1 V between the radio audio mute signal terminal 37 and ground.
    3. ⇒If greater than the specified value, test the circuit for a short to voltage. If the circuit tests normal, replace the T3 Audio Amplifier.
  3. Ignition OFF, test for greater than 20 Ω between the radio audio mute signal terminal 37 and ground.
    4. ⇒If less than the specified value, test the circuit for a short to ground. If the circuit tests normal, replace the T3 Audio Amplifier.
  4. Ignition OFF, disconnect the X3 harness connector at the T3 Audio Amplifier.
  5. Test for less than 5 Ω between the radio X1 terminal 37 to the amplifier X3 terminal 6.
    6. ⇒If greater than specified range, test the circuit for an open/high resistance.
  6. If all circuits test normal, replace the A11 Radio.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for radio and amplifier replacement, setup, and programming

   


© Copyright Chevrolet. All rights reserved
   


© Copyright Chevrolet. All rights reserved