AutoCodes – Generic – B127C:04

B127C:04 Code - Microphone 2 Input Signal Circuit Open/High Resistance

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: B127C:04 indicates Microphone 2 Input Signal Circuit Open/High Resistance.
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 1,266

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 B127C:04 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 an open is detected on the specified (+) or (−) signal circuit for more than 1.5 seconds

OBDII Code B127C:04 - Microphone 2 Input Signal Circuit Open/High Resistance - AutoCodes.com — B127C:04 Code - Microphone 2 Input Signal Circuit Open/High Resistance

What does this mean?

What are the Possible Causes of the DTC B127C:04?

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 B127C:04?

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 B127C:04 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 B127C:04 Code

1. What does the OBDII code B127C:04 mean?

The code B127C:04 indicates an issue with Microphone 2â€™s input signal circuit, specifically an open circuit or high resistance detected.

2. What are the symptoms of the B127C:04 code?

Symptoms may include poor voice recognition performance, inoperative hands-free calling, or no audio input from Microphone 2.

3. What causes the B127C:04 code to appear?

Common causes include a damaged microphone, faulty wiring or connectors, corrosion in the circuit, or a malfunctioning audio control module.

4. How is the B127C:04 code diagnosed?

A technician will inspect the wiring and connectors, test the microphone for continuity, and use a scan tool to monitor the circuit's signal.

5. Can I still use my car if the B127C:04 code is present?

Yes, the vehicle is typically drivable, but features like voice commands or hands-free calling may not work properly.

6. How do I fix the B127C:04 code?

Repairs may involve replacing the microphone, repairing or replacing damaged wiring, cleaning corroded connectors, or updating/replacing the audio control module.

7. How much does it cost to repair the B127C:04 code?

The repair cost varies depending on the exact issue, but it might range from $50 for a simple wiring fix to $300+ for replacing the microphone or module.

8. Can a software update resolve the B127C:04 code?

In some cases, a software update for the audio or infotainment system might resolve the issue if itâ€™s related to system miscommunication.

9. Where is Microphone 2 typically located in a car?

Microphone 2 is often located in the overhead console, near the rearview mirror, or integrated into the headliner.

10. Can I clear the B127C:04 code without fixing the problem?

Clearing the code without addressing the underlying issue may temporarily remove it, but the code will likely return once the system detects the fault again.