AutoCodes – Generic – B124A

B124A Code - Automatic High Beam Mirror

Quick Answer

This Diagnostic Trouble Code (DTC) is stored when the Main Body ECU (Multiplex Network Body ECU) detects a malfunction in the Forward Recognition Camera. Common causes include Faulty Forward Recognition Camera, Forward Recognition Camera harness is open or shorted, Forward Recognition Camera 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: B124A indicates Automatic High Beam Mirror.
Common causes: Common causes include Faulty Forward Recognition Camera, Forward Recognition Camera harness is open or shorted, Forward Recognition Camera 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 1,677

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 19, 2024

Description
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
FAQs
Comments
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Code B124A Description

This Diagnostic Trouble Code (DTC) is stored when the Main Body ECU (Multiplex Network Body ECU) detects a malfunction in the Forward Recognition Camera.

OBDII Code B124A - Automatic High Beam Mirror - AutoCodes.com — B124A Code - Automatic High Beam Mirror

What does this mean?

What are the Possible Causes of the DTC B124A?

Faulty Forward Recognition Camera
Forward Recognition Camera harness is open or shorted
Forward Recognition Camera circuit poor electrical connection
Faulty Main Body ECU (Multiplex Network Body ECU)

How to Fix the DTC B124A?

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

When replacing the forward recognition camera, always replace it with a new one. If a forward recognition camera that was installed on another vehicle is used, the information stored in the forward recognition camera will not match the information from the vehicle. As a result, a DTC may be stored.
If the forward recognition camera has been replaced with a new one, be sure to perform Recognition Camera/Target Position Memory and Recognition Camera Axis Adjust.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the B124A 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 B124A code?

Need more information on how to fix the B124A code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the B124A code diagnosed by a professional: Find a repair shop in your area

Information for Specific Makes

B124A Lexus — Automatic High Beam Mirror
B124A Scion — Automatic High Beam Mirror
B124A Toyota — Automatic High Beam Mirror

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 B124A Code

1. What does the OBDII code B124A mean?

The B124A code indicates an issue with the Automatic High Beam Mirror system, which is responsible for controlling automatic high beam functionality based on driving conditions.

2. What are the common symptoms of the B124A code?

Symptoms include the automatic high beam feature not functioning, high beams staying on or not activating automatically, and potential warning lights on the dashboard.

3. What causes the B124A code to appear?

Common causes include a malfunctioning high beam mirror sensor, wiring or connector issues, or software glitches in the vehicle's lighting control module.

4. Can a dirty windshield cause the B124A code?

Yes, a dirty or damaged windshield can obstruct the sensor's view and trigger the B124A code by affecting the automatic high beam system's performance.

5. How is the B124A code diagnosed?

A mechanic typically uses an OBDII scanner to retrieve the code and checks the high beam mirror sensor, wiring, and connectors for damage or faults.

6. Can I still drive my car with the B124A code?

Yes, you can usually drive with this code, but the automatic high beam feature may not work, requiring manual control of your high beams.

7. How do you fix the B124A code?

Repairs may involve cleaning or replacing the high beam mirror sensor, fixing damaged wiring, clearing obstructions, or updating the lighting control module software.

8. How much does it cost to repair the B124A code?

Repair costs vary depending on the issue, ranging from $50 for a simple sensor cleaning to over $200 for sensor replacement or wiring repairs.

9. Can resetting the system clear the B124A code?

In some cases, disconnecting the battery or using an OBDII scanner to reset the system may temporarily clear the code, but the underlying issue must be addressed to prevent recurrence.

10. How can I prevent the B124A code from occurring?

Regularly clean your windshield, ensure the high beam mirror sensor is unobstructed, and maintain your vehicle's electrical system to help prevent this code.