AutoCodes – GMC – B127D 2015 GMC Sierra

B127D 2015 GMC Sierra Code - Microphone 3 Input Signal Circuit

Quick Answer

The active noise cancellation system uses three microphones in the vehicle headliner: one above each front seating position, and one above the rear seat. Common causes include Faulty Radio Volume Compensator Interior Noise Microphone, Radio Volume Compensator Interior Noise Microphone harness is open or shorted, Radio Volume Compensator Interior Noise Microphone circuit poor electrical connection. Severity is Low - monitor the vehicle and repair when practical. The vehicle can usually be driven if no severe symptoms are present, but symptoms should be checked before extended driving.

What it means: B127D 2015 GMC Sierra indicates Microphone 3 Input Signal Circuit.
Common causes: Common causes include Faulty Radio Volume Compensator Interior Noise Microphone, Radio Volume Compensator Interior Noise Microphone harness is open or shorted, Radio Volume Compensator Interior Noise Microphone circuit poor electrical connection.
Severity: Low - monitor the vehicle and repair when practical.
Can I drive?: The vehicle can usually be driven if no severe symptoms are present, but symptoms should be checked before extended driving.

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Code Popularity 235

How popular is this code, among other codes? Low

Repair Importance Level

Low (Monitor) (1 / 3)

Repair Difficulty Level

Intermediate (2 / 3)

What is this?

Table of contents Created and updated by William Orellana on Nov 29, 2024

Description
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
FAQs
Comments
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Code B127D 2015 GMC Sierra Description

The active noise cancellation system uses three microphones in the vehicle headliner: one above each front seating position, and one above the rear seat. The Audio Amplifier provides a bias voltage to each microphone (+) and (-) signal circuit for the operation of the microphone. The microphones monitor the vehicle cabin for undesirable engine sounds. The Audio Amplifier uses the microphone inputs and an engine RPM signal to determine the frequency of the undesirable sound. The Diagnostic Trouble Code (DTC) will be set when a fault is detected on the specified (+) or (−) signal circuit for more than 1.5 seconds.

OBDII Code B127D 2015 GMC Sierra - Microphone 3 Input Signal Circuit - AutoCodes.com — B127D 2015 GMC Sierra Code - Microphone 3 Input Signal Circuit

What does this mean?

What are the Possible Causes of the DTC B127D 2015 GMC Sierra?

Faulty Radio Volume Compensator Interior Noise Microphone
Radio Volume Compensator Interior Noise Microphone harness is open or shorted
Radio Volume Compensator Interior Noise Microphone circuit poor electrical connection
Faulty Audio Amplifier

How to Fix the DTC B127D 2015 GMC Sierra?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What does this mean?

Code Tech Notes

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.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the B127D 2015 GMC Sierra code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

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About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.

Frequently Asked Questions about B127D 2015 GMC Sierra Code

1. What does the OBDII code B127D mean for a 2015 GMC Sierra?

The code B127D refers to an issue with the Microphone 3 Input Signal Circuit, indicating a malfunction or irregularity in the audio system's microphone wiring or components.

2. What are the symptoms of code B127D in a 2015 GMC Sierra?

Common symptoms include poor voice recognition, inoperative hands-free calling, degraded audio quality during calls, or no response from the microphone.

3. What causes code B127D to appear in a 2015 GMC Sierra?

Potential causes include a faulty or disconnected microphone, damaged wiring, corroded connectors, or a malfunctioning infotainment system module.

4. How can I diagnose the B127D code on my GMC Sierra?

Start by inspecting the microphone and its connections for damage, checking the wiring harness, and using a scan tool to verify the circuit's operation and confirm the fault.

5. Can a bad microphone trigger the B127D code?

Yes, a defective or non-functional microphone can cause the B127D code to appear since the circuit may not be receiving the proper input signal.

6. Is the B127D code serious for my 2015 GMC Sierra?

While not critical for vehicle operation, the code can affect hands-free communication and voice command features, which may be inconvenient or distracting.

7. How do I fix the B127D code on my GMC Sierra?

Repairs may involve replacing the faulty microphone, repairing damaged wiring, cleaning corroded connectors, or reprogramming/updating the infotainment module.

8. Can a software update fix the B127D code?

In some cases, a software update for the infotainment system may resolve the issue if it is related to a programming glitch rather than a hardware fault.

9. Where is Microphone 3 located in a 2015 GMC Sierra?

Microphone 3 is typically part of the vehicle's overhead console or integrated into the headliner, depending on the trim level and audio system configuration.

10. Can I clear the B127D code without fixing the problem?

Clearing the code with a scan tool may temporarily remove it, but the issue will likely return unless the underlying problem is resolved.