AutoCodes – Generic – B1278

B1278 Code - Headlight Switch ON Position Circuit Malfunction

Quick Answer

The Multiplex Integrated Control Unit (MICU) monitors the Headlight Switch Position. Common causes include Faulty Combination Headlight Switch, Combination Headlight Switch harness is open or shorted, Combination Headlight Switch circuit poor electrical connection. 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: B1278 indicates Headlight Switch ON Position Circuit Malfunction.
Common causes: Common causes include Faulty Combination Headlight Switch, Combination Headlight Switch harness is open or shorted, Combination Headlight Switch circuit poor electrical connection.
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.

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Code Popularity 9,896

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

What is this?

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

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code B1278 Description

The Multiplex Integrated Control Unit (MICU) monitors the Headlight Switch Position. The MICU sets the OBDII code when the Headlight Switch Position is not to factory specifications.

OBDII Code B1278 - Headlight Switch ON Position Circuit Malfunction - AutoCodes.com — B1278 Code - Headlight Switch ON Position Circuit Malfunction

What does this mean?

What are the Possible Causes of the DTC B1278?

Faulty Combination Headlight Switch
Combination Headlight Switch harness is open or shorted
Combination Headlight Switch circuit poor electrical connection
Faulty Multiplex Integrated Control Unit (MICU)

How to Fix the DTC B1278?

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 is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the B1278 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 B1278 code?

Need more information on how to fix the B1278 code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the B1278 code diagnosed by a professional: Find a repair shop in your area

Information for Specific Makes

B1278 Acura — Headlight Switch ON Position Circuit Malfunction
B1278 Honda — Headlight Switch ON Position Circuit Malfunction

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 B1278 Code

1. What are common symptoms of OBDII code B1278 (Headlight Switch ON Position Circuit Malfunction)?

- Common symptoms include the headlights not turning on when the switch is in the ON position, flickering headlights, or the headlights staying on even when the switch is turned off.

2. What are possible causes of OBDII code B1278?

- Possible causes include a faulty headlight switch, damaged wiring or connectors in the headlight circuit, or a malfunctioning headlight control module.

3. How can I diagnose the issue related to OBDII code B1278?

- You can use a diagnostic scanner to read the code and further investigate the headlight switch, wiring, and control module for any visible damage or irregularities.

4. Can a DIY enthusiast repair OBDII code B1278 at home?

- Repairing this code may involve replacing the headlight switch, repairing damaged wiring, or replacing the headlight control module, which can be challenging for DIY enthusiasts. Professional help may be needed.

5. Are there any quick tips to troubleshoot OBDII code B1278?

- Before conducting any repairs, check the headlight fuse, ensure the bulbs are functioning properly, and inspect the wiring for any visible damage as a quick initial troubleshooting step.

6. Is it safe to drive with OBDII code B1278 present?

- It is not recommended to drive with this code present, as malfunctioning headlights can compromise your visibility on the road, especially at night or in low-light conditions.

7. How much does it typically cost to repair OBDII code B1278?

- The cost of repairing this code can vary depending on the specific issue causing it, but it may range from $100 to $300 for parts and labor if professional assistance is required.

8. Can OBDII code B1278 be intermittent or permanent?

- This code can be intermittent, meaning the issue causing the malfunction may come and go, or it can be a permanent issue that requires immediate attention.

9. Will resetting the OBDII system clear code B1278?

- Resetting the OBDII system may temporarily clear the code, but if the underlying issue causing the malfunction is not addressed, the code is likely to reappear.

10. How can I prevent OBDII code B1278 from recurring in the future?

- Regularly inspecting the headlight system, ensuring proper maintenance, and addressing any issues promptly can help prevent the recurrence of OBDII code B1278.