AutoCodes – GMC – B257A 2018 GMC Sierra

B257A 2018 GMC Sierra Code - Headlamp Switch Input Signals Correlation Malfunction

Quick Answer

For headlamp operation, the Body Control Module (BCM) monitors three signal circuits from the headlamp switch. Common causes include Faulty Headlamp Switch, Headlamp Switch harness is open or shorted, Headlamp 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: B257A 2018 GMC Sierra indicates Headlamp Switch Input Signals Correlation Malfunction.
Common causes: Common causes include Faulty Headlamp Switch, Headlamp Switch harness is open or shorted, Headlamp 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 178

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 May 26, 2023

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code B257A 2018 GMC Sierra Description

For headlamp operation, the Body Control Module (BCM) monitors three signal circuits from the headlamp switch. When the headlamp switch is in the AUTO position, the three signal circuits are unaffected and the BCM relies on the ambient light sensor input to turn the headlamps and daytime running lamps ON and OFF. When the headlamp switch is placed in the OFF position, the headlamp switch headlamps OFF signal circuit is grounded, indicating to the BCM that the exterior lamps should be turned OFF. With the headlamp switch in the PARK LAMPS position, the headlamp switch park lamps ON signal circuit is grounded, indicating that the park lamps have been requested. When the headlamp switch is in the HEADLAMP position, both the headlamp switch park lamps ON signal circuit and the headlamp switch headlamps ON signal circuit are grounded. The BCM responds by commanding the park lamps and low beam headlamps ON.

OBDII Code B257A 2018 GMC Sierra - Headlamp Switch Input Signals Correlation Malfunction - AutoCodes.com — B257A 2018 GMC Sierra Code - Headlamp Switch Input Signals Correlation Malfunction

What does this mean?

What are the Possible Causes of the DTC B257A 2018 GMC Sierra?

Faulty Headlamp Switch
Headlamp Switch harness is open or shorted
Headlamp Switch circuit poor electrical connection
Faulty Body Control Module (BCM)

How to Fix the DTC B257A 2018 GMC Sierra?

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 B257A 2018 GMC Sierra 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 B257A 2018 GMC Sierra code?

Need more information on how to fix the B257A 2018 GMC Sierra code? Get Access to Factory Service Manuals

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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 B257A 2018 GMC Sierra Code

1. What are the common symptoms of OBDII code B257A in a 2018 GMC Sierra?

The common symptoms of code B257A include issues with the headlamp switch functionality, such as erratic behavior or failure to turn the headlamps on or off.

2. What can cause the Headlamp Switch Input Signals Correlation Malfunction in a 2018 GMC Sierra?

The malfunction can be caused by a faulty headlamp switch, wiring issues, a defective control module, or a poor connection in the headlamp circuit.

3. How can I diagnose the cause of OBDII code B257A in my 2018 GMC Sierra?

Diagnosing the issue may involve checking the headlamp switch for proper operation, inspecting the wiring for any damage, testing the control module, and ensuring all connections in the headlamp circuit are secure.

4. Can I still drive my 2018 GMC Sierra with OBDII code B257A?

It is generally safe to drive your vehicle with this code, but it is important to address the issue promptly to ensure proper functioning of the headlamp system.

5. How can I repair OBDII code B257A in my 2018 GMC Sierra?

Repairing the code may involve replacing the headlamp switch, repairing any damaged wiring, resetting the control module, or addressing any loose connections in the headlamp circuit.

6. Will resetting the OBDII code B257A in my 2018 GMC Sierra make it go away permanently?

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

7. Can a DIY enthusiast fix OBDII code B257A in a 2018 GMC Sierra?

Depending on your skill level and access to tools, you may be able to address simpler causes such as loose connections or minor wiring issues. However, more complex issues may require professional assistance.

8. Is it expensive to repair OBDII code B257A in a 2018 GMC Sierra?

The cost of repair can vary based on the specific cause of the malfunction. Simple fixes like tightening connections may be relatively inexpensive, while replacing a faulty control module or switch can be more costly.

9. Can extreme weather conditions trigger OBDII code B257A in a 2018 GMC Sierra?

Extreme weather conditions, such as excessive heat or moisture, can potentially exacerbate underlying issues leading to the code. Ensuring proper weatherproofing and insulation can help prevent such problems.

10. How often should I check for OBDII code B257A in my 2018 GMC Sierra?

It is a good practice to periodically scan for codes, especially if you notice any issues with the headlamp system. Regular maintenance checks can help catch and address problems early on.