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DTC B1278 or B1279

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 B1278 01: Left Auxiliary Input Signal Circuit Short to Battery

DTC B1278 02: Left Auxiliary Input Signal Circuit Short to Ground

DTC B1279 01: Right Auxiliary Input Signal Circuit Short to Battery

DTC B1279 02: Right Auxiliary Input Signal Circuit Short to Ground

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Right Auxiliary Audio Signal

B1279 02*

*

B1279 01*

-

Left Auxiliary Audio Signal

B1278 02 **

**

B1278 01 **

-

Auxiliary Audio Common Ground

--

1

-

-

1. No or distorted audio from both sides.

*. No or distorted right side audio

**. No or distorted left side audio

Circuit/System Description

A remote 3.5 mm auxiliary stereo jack allows playback of audio signals from remote devices (e.g., laptop computer, IPOD, MP3 player, etc.). When a remote device audio mini-plug is inserted in the remote auxiliary jack, an internal mechanical switch closes completing the aux jack detect circuit to the radio. The radio automatically detects the input through the circuit and the device begins playing. The radio receives the devices audio signals on the auxiliary input 1 (left) signal circuit and auxiliary input 2 (right) signal circuit. If equipped with a Multimedia Player Interface Module, the auxiliary inputs that may normally connect directly to the radio will have the Multimedia Player Interface Module inline of those connections. This means that the auxiliary inputs for the radio connect to the Multimedia Player Interface Module, and the Multimedia Player Interface Module connects to the radio, passing along the audio and USB signals. Both the Radio and the Multimedia Player Interface Module can set these DTCs.

The auxiliary audio jack has an internal mechanical detection switch that will connect the detection signal on the auxiliary audio jack to ground when an auxiliary mini-plug is inserted.

Conditions for Running the DTC
    • Ignition in ON or Accessory position.
    • The system voltage is at least 9.5 V and no more than 15.5 V.

Conditions for Setting the DTC
    • The radio detects a short to battery on the auxiliary input 1 signal circuit or auxiliary input 2 signal circuit.
    • The radio detects a short to ground on the auxiliary input 1 signal circuit or auxiliary input 2 signal circuit.
    • All the above conditions are present for greater than 250 mS.

Action Taken When the DTC Sets

No audio is heard from the remote audio device.

Conditions for Clearing the DTC
    • The conditions for setting the DTC are no longer present on the auxiliary input signal circuits.
    • A history DTC clears after 50 malfunction-free ignition cycles.

Diagnostic Aids
    • This DTC may be stored as a history DTC without affecting the operation of the module.
    • If stored only as a history DTC and not retrieved as a current DTC, do not replace the module.

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 Testing

Without Multimedia Player Interface Module

  1. Ignition OFF, disconnect the harness connector at the auxiliary audio jack.
  2. Ignition ON, test for less than 1 V between the terminals listed below and ground:
    3. • Left auxiliary audio signal terminal 2
    • Right auxiliary audio signal terminal 4
    • Auxiliary audio common signal terminal 5
    ⇒If greater than the specified value, test the circuit for a short to voltage. If the circuit tests normal, replace the A11 Radio.
  3. Ignition OFF, test for infinite resistance between the terminals listed below and ground:
    4. •  Left auxiliary audio signal terminal 2
    • Right auxiliary audio signal terminal 4
    ⇒If less than the specified value, test the circuit for a short to ground. If the circuit tests normal, replace the A11 Radio.
  4. If all of the circuits test normal, replace the X83 Auxiliary Audio Input.

With Multimedia Player Interface Module (KTA/KTB) DTC Set in Radio

  1. Ignition OFF, disconnect the harness connector at the Multimedia Player Interface Module module.
  2. Ignition ON, test for less than 1 V between the terminals listed below and ground:
    3. • Left auxiliary audio signal terminal 14
    • Right auxiliary audio signal terminal 15
    • Auxiliary audio common signal terminal 4
    • Auxiliary audio drain wire terminal 5
    ⇒If greater than the specified value, test the circuit for a short to voltage. If the circuit tests normal, replace the A11 Radio.
  3. Ignition OFF, test for infinite resistance between the terminals listed below and ground:
    4. •  Left auxiliary audio signal terminal 14
    • Right auxiliary audio signal terminal 15
    ⇒If less than the specified value, test the circuit for a short to ground. If the circuit tests normal, replace the A11 Radio.
  4. If all of the circuits test normal, replace the X83 Auxiliary Audio Input.

With Multimedia Player Interface Module (KTA/KTB) DTC Set in Multimedia Player Interface Module

  1. Ignition OFF, disconnect the harness connector at the X83 Auxiliary Audio Input.
  2. Ignition ON, test for less than 1 V between the terminals listed below and ground:
    3. • Left auxiliary audio signal terminal 2
    • Right auxiliary audio signal terminal 4
    • Auxiliary audio common signal terminal 5
    ⇒If greater than the specified value, test the circuit for a short to voltage. If the circuit tests normal, replace the Multimedia Player Interface Module.
  3. Ignition OFF, test for infinite resistance between the terminals listed below and ground:
    4. •  Left auxiliary audio signal terminal 2
    • Right auxiliary audio signal terminal 4
    ⇒If less than the specified value, test the circuit for a short to ground. If the circuit tests normal, replace the Multimedia Player Interface Module.
  4. If all of the circuits test normal, replace the X83 Auxiliary Audio Input.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for Radio and Multimedia Player Interface Module replacement, setup, and programming

   


© Copyright Chevrolet. All rights reserved
   


© Copyright Chevrolet. All rights reserved