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Engine-Codes – Generic – B143B

B143B Code - Microphone 1 Circuit Low

Quick Answer

The diagnostic trouble code B143B indicates a problem with the Microphone 1 circuit, specifically signaling that the Hands Free Module has detected a low voltage or an open circuit condition in the microphone system. Common causes include Faulty Inside Rear View Mirror, which houses the microphone, Inside Rear View Mirror harness is open or shorted, disrupting the circuit, Poor electrical connection within the Inside Rear View Mirror circuit. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means
B143B indicates Microphone 1 Circuit Low.
Common causes
Common causes include Faulty Inside Rear View Mirror, which houses the microphone, Inside Rear View Mirror harness is open or shorted, disrupting the circuit, Poor electrical connection within the Inside Rear View Mirror circuit.
Severity
High - diagnose this code as soon as possible.
Can I drive?
Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.
What is this?
Table of contents Created and updated by William Orellana on Nov 05, 2025
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Code B143B Description

The diagnostic trouble code B143B indicates a problem with the Microphone 1 circuit, specifically signaling that the Hands Free Module has detected a low voltage or an open circuit condition in the microphone system. This system is crucial for hands-free communication, allowing drivers to make phone calls or interact with voice-activated features without taking their hands off the wheel. In many vehicles, the microphone is integrated into the Inside Rear View Mirror, which means that any issues with the mirror can directly impact the microphone's functionality. If this code is triggered, it suggests that the microphone is not operating within the factory specifications set by the manufacturer. Ignoring this code can lead to several long-term effects, including a complete failure of the hands-free system, which can compromise driver safety and convenience. Additionally, if the microphone is malfunctioning, it may not pick up voice commands effectively, leading to frustration and potential distractions while driving. Over time, this could also lead to further electrical issues within the vehicle's audio or communication systems. Addressing the B143B code promptly is essential to ensure that all hands-free functionalities operate correctly and to maintain the overall integrity of the vehicle’s electronic systems.
OBDII Code B143B - Microphone 1 Circuit Low
B143B Code - Microphone 1 Circuit Low

Common Causes of B143B

  1. Faulty Inside Rear View Mirror, which houses the microphone
  2. Inside Rear View Mirror harness is open or shorted, disrupting the circuit
  3. Poor electrical connection within the Inside Rear View Mirror circuit
  4. Faulty Hands Free Module that processes microphone signals
  5. Damaged wiring or connectors leading to the microphone

Symptoms of B143B

  1. Engine Light ON (or Service Engine Soon Warning Light)
  2. Inability to use voice commands for navigation or phone calls
  3. Static or poor audio quality during hands-free calls
  4. Intermittent or complete loss of hands-free functionality
  5. Feedback noise or echo during calls

How to Fix B143B

  1. Perform a visual inspection of the Inside Rear View Mirror and its wiring for signs of damage or disconnection.
  2. Test the microphone circuit for continuity and check for any shorts or opens using a multimeter.
  3. If the microphone is integrated into the Inside Rear View Mirror, consider replacing the entire mirror assembly if it is found to be faulty.
  4. Inspect and repair any damaged wiring or connectors that may be affecting the microphone circuit.
  5. Clear the diagnostic trouble code and test the system to ensure proper functionality of the hands-free features.

Cost to Fix B143B

The cost to diagnose and repair the B143B code can vary significantly based on the specific vehicle make and model, as well as the labor rates in your area. Typically, parts such as a new Inside Rear View Mirror can range from $100 to $300, while labor costs can range from $80 to $150 per hour at most shops. Dealerships may charge higher rates, while independent shops may offer more competitive pricing. Overall, you can expect the total repair cost to fall between $150 and $500, depending on the complexity of the issue and the parts needed.

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Code B143B Information for Specific Makes

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.

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