AutoCodes – GMC – B127D GMC

B127D GMC 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 GMC 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 1,081

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

What does this mean?

What are the Possible Causes of the DTC B127D GMC?

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 GMC?

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 GMC 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.

Need more information about the B127D GMC code?

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Need Help with the Code?

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Information for Specific GMC Models

B127D 2014 GMC Sierra — Microphone 3 Input Signal Circuit
B127D 2015 GMC Sierra — Microphone 3 Input Signal Circuit
B127D 2016 GMC Sierra — Microphone 3 Input Signal Circuit
B127D 2017 GMC Sierra — Microphone 3 Input Signal Circuit
B127D 2018 GMC Sierra — Microphone 3 Input Signal Circuit

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 GMC Code

1. What are the common symptoms of OBDII code B127D GMC (Microphone 3 Input Signal Circuit)?

- Common symptoms include a malfunctioning microphone, inoperative hands-free calling feature, and issues with voice command recognition.

2. What can cause the OBDII code B127D GMC to trigger?

- The code may be triggered by a faulty microphone, wiring issues in the microphone circuit, or a problem with the hands-free calling system.

3. How can I diagnose the Microphone 3 Input Signal Circuit issue?

- Diagnosis involves checking the microphone for physical damage, testing the wiring for continuity, and using a scan tool to monitor the microphone input signal.

4. Is it safe to continue driving with the B127D GMC trouble code?

- It is generally safe to continue driving with this code, but it is recommended to address the issue promptly to restore hands-free calling functionality.

5. Can I repair the Microphone 3 Input Signal Circuit issue myself?

- Depending on your automotive repair skills, you may be able to repair the issue yourself by replacing the microphone, repairing wiring issues, or resetting the hands-free calling system.

6. How much does it typically cost to fix the B127D GMC trouble code?

- The cost of fixing this code can vary depending on the cause of the issue, but it may range from $50 to $200 for parts and labor.

7. Will resetting the OBDII code B127D GMC make the issue go away permanently?

- Resetting the code may temporarily clear the warning light, but the underlying issue with the microphone input signal circuit must be diagnosed and repaired to prevent the code from reoccurring.

8. Are there any preventive measures to avoid triggering the B127D GMC trouble code?

- Regularly inspecting the hands-free calling system, ensuring proper microphone functionality, and avoiding physical damage to the microphone can help prevent this code from being triggered.

9. Can a faulty microphone cause other issues in the vehicle apart from triggering the B127D GMC trouble code?

- Yes, a faulty microphone can affect the hands-free calling feature, voice recognition systems, and overall convenience of using communication features in the vehicle.

10. How long does it typically take to repair the Microphone 3 Input Signal Circuit issue?

- The repair time can vary based on the cause of the issue and the complexity of the repair, but it may take anywhere from 1 to 3 hours to fix the problem.