DTC B1278 or B1279. Cadillac CTS 2009

For 1990-2009 cars only

Makes 🢒 Cadillac 🢒 2009 🢒 CTS 🢒 Driver Information and Entertainment 🢒 Cellular, Entertainment, and Navigation 🢒 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: Auxiliary Input 1 Signal Circuit Short to Battery

DTC B1278 02: Auxiliary Input 1 Signal Circuit Short to Ground

DTC B1279 01: Auxiliary Input 2 Signal Circuit Short to Battery

DTC B1279 02: Auxiliary Input 2 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 devices 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.

Conditions for Running the DTC

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

•	The ignition must be in the RUN or ACC position.

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

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

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

Ignition OFF, disconnect the auxiliary audio jack harness connector.
Ignition ON, test for less than 1 volt between the left axuiliary audio signal terminal 6, to ground.

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

Test for less than 1 volt between the right axuiliary audio signal terminal 7, to ground.

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

Test for less than 1 volt between the axuiliary audio common signal terminal 5, to ground.

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

Ignition OFF, test for infinite resistance from the left axuiliary audio signal terminal 6, to ground.

⇒	If less than the specified value, test the circuit for a short to ground. If the circuit tests normal, replace the radio.

Test for infinite resistance from the right axuiliary audio signal terminal 7, to ground.

⇒	If less than the specified value, test the circuit for a short to ground. If the circuit tests normal, replace the radio.

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