Service Information

Volt

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 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

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 opens. The radio detects the device, switches to AUX as the audio source, and the device begins playing. Audio signals from the device are sent to the radio from the auxiliary input jack via the left, right, and common audio signal circuits.

Conditions for Running the DTC

•	Ignition in RUN or ACC position.

•	The system voltage is at least 9.5 V and no more than 15.5 V.

Conditions for Setting the DTC

B 1278

The radio detects a short to battery or short to ground on the left auxiliary audio signal circuit.

B 1279

The radio detects a short to battery or short to ground on the right auxiliary audio signal circuit.

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

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

Vehicle OFF, disconnect the X1 harness connector at the X83 auxiliary audio jack.
Vehicle in Service Mode, test for less than 1 V between the terminals listed below and ground:

•	signal terminal 1

•	signal terminal 2

⇒	If greater than the specified value, test the circuit for a short to voltage. If the circuit tests normal, replace the A11 radio.

Vehicle OFF, disconnect the X1 harness connector at the radio. Test for infinite resistance between the circuits listed below and ground:

•	auxiliary audio common circuit terminal 23

•	left auxiliary audio circuit terminal 24

•	right auxiliary audio circuit terminal 10

⇒	If not the specified value, test the signal circuit for a short to ground.

If all circuits test normal, replace the X83 auxiliary audio jack.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

•	Audio Disc Player, USB, Auxiliary In, and Memory Card Receptacle Replacement

•	Control Module References for radio replacement, programming and setup