B1277

DTC B1277, B127C, or B127D

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions Diagnostic Procedure Instructionsprovide an overview of each diagnostic category.

DTC Descriptors
DTC B1277 01
- Microphone 1 (LF) Input Signal Circuit Short to Battery

DTC B1277 02
- Microphone 1 (LF) Input Signal Circuit Short to Ground

DTC B1277 04
- Microphone 1 (LF) Input Signal Circuit Open

DTC B1277 1A
- Microphone 1 (LF) Input Signal Circuit Bias Level Out of Range

DTC B127C 01
- Microphone 2 (RF) Input Signal Circuit Short to Battery

DTC B127C 02
- Microphone 2 (RF) Input Signal Circuit Short to Ground

DTC B127C 04
- Microphone 2 (RF) Input Signal Circuit Open

DTC B127C 1A
- Microphone 2 (RF) Input Signal Circuit Bias Level Out of Range

DTC B127D 01
- Microphone 3 (RR) Input Signal Circuit Short to Battery

DTC B127D 02
- Microphone 3 (RR) Input Signal Circuit Short to Ground

DTC B127D 04
- Microphone 3 (RR) Input Signal Circuit Open

DTC B127D 1A
- Microphone 3 (RR) Input Signal Circuit Bias Level Out of Range

Circuit/System Description

The active noise cancellation system uses three microphones in the vehicle headliner: one above each front seating position, and another above the right side of the second row seat. The amplifier provides a bias voltage to each microphone (+) and (-) signal circuits for operation of the microphone. The microphones monitor the vehicle cabin for undesirable engine sounds. The amplifier uses the microphone inputs and an engine RPM signal to determine the frequency of the undesirable sound.

Conditions for Running the DTC

The amplifier performs a self diagnostic of the microphone circuits 16 seconds after initial power up, then periodically every 400 milliseconds thereafter.

Conditions for Setting the DTC

DTC B1277 01, B127C 01, B127D 01
* DTC B1325 is not current
* A short to voltage is detected on the specified (+) or (-) signal circuit for more than 1.5 seconds

DTC B1277 02, B127C 02, B127D 02
* DTC B1325 is not current
* A short to voltage is detected on the specified (+) or (-) signal circuit for more than 1.5 seconds

DTC B1277 04, B127C 04, B127D 04
* DTC B1325 is not current
* An open is detected on the specified (+) or (-) signal circuit for more than 1.5 seconds

DTC B1277 1A, B127C 1A, B127D 1A
* DTC B1325 is not current
* An out of range voltage is detected on the specified (+) or (-) signal circuit for more than 1.5 seconds

Action Taken When the DTC Sets

The active noise cancellation system is disabled.

Conditions for Clearing the DTC

* A current DTC clears when the self diagnostic passes on the next ignition cycle.
* A history DTC clears when the ignition cycle counter reaches the reset threshold without a repeat of the malfunction.

Diagnostic Aids

* Installation of aftermarket replacement speakers, additional speakers/subwoofers, or aftermarket exhaust systems can cause undesirable behavior of the active noise cancellation system.
* The noise reduction microphones have foam blocks above them to seal the microphones and aid in the reduction of headliner vibration. Missing or out of place foam blocks can impact system performance.

Reference Information
Schematic Reference

Active Noise Cancellation Schematics Active Noise Cancellation Schematics
Connector End View Reference

Component Connector End Views Connector End Views By Name
Description and Operation

Active Noise Cancellation Description and Operation Active Noise Cancellation
Electrical Information Reference

* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs

Scan Tool Reference

Control Module References Programming and Relearningfor scan tool information

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the appropriate microphone.
2. Ignition ON Radio ON , test for 0.47-2.75 V between the microphone (-) signal circuit terminal A and ground.

• If greater than the specified range, test the circuit for a short to voltage. If the circuit tests normal, replace the amplifier.
• If less than the specified range, test the circuit for an open/high resistance or a short to ground. If the circuit tests normal, replace the amplifier.

3. Test for 5.75-8.03 V between the microphone (+) signal circuit terminal B and ground.

• If greater than the specified range, test the circuit for a short to voltage. If the circuit tests normal, replace the amplifier.
• If less than the specified range, test the circuit for an open/high resistance or a short to ground. If the circuit tests normal, replace the amplifier.

4. If all circuits test normal, replace the appropriate microphone.

Repair Instructions

Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.

* Radio Volume Compensator Interior Noise Microphone Replacement
* Control Module References Programming and Relearningfor amplifier replacement, setup, and programming