AutoCodes – GMC – B257A 2017 GMC Sierra

B257A 2017 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 2017 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.

Save to My Repairs My Repairs

AI answers can be wrong. Verify repairs with testing. Open full chat

Code Popularity 192

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
Add Comment

💬 Need more help? Ask Coddy for instant answers — it's free!

Code B257A 2017 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 2017 GMC Sierra - Headlamp Switch Input Signals Correlation Malfunction - AutoCodes.com — B257A 2017 GMC Sierra Code - Headlamp Switch Input Signals Correlation Malfunction

What does this mean?

What are the Possible Causes of the DTC B257A 2017 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 2017 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 2017 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 2017 GMC Sierra code?

Need more information on how to fix the B257A 2017 GMC Sierra code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the B257A 2017 GMC Sierra code diagnosed by a professional: Find a repair shop in your area

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 2017 GMC Sierra Code

What does the OBDII code B257A mean for a 2017 GMC Sierra?

B257A indicates a malfunction related to the headlamp switch input signals, meaning there is a correlation issue between the headlamp switch and the vehicle's computer.

What are common symptoms of the B257A code?

Common symptoms include malfunctioning headlights, dashboard warning lights, and potential issues with other lighting functions such as fog lights or turn signals.

What could cause the B257A code to trigger?

Causes may include a faulty headlamp switch, wiring issues, poor connections, or problems with the body control module (BCM).

How can I diagnose the B257A code?

Start by using an OBDII scanner to confirm the code, then visually inspect the headlamp switch and related wiring for damage or corrosion. Test the switch's functionality and check for any other related codes.

What repair steps should I take if I get the B257A code?

Repair steps may include replacing the headlamp switch if faulty, repairing any damaged wiring, or reprogramming or replacing the BCM if necessary.

Is it safe to drive with the B257A code?

While it might be safe to drive, you may experience issues with your headlights or other lighting systems, which could pose a safety risk. It's best to address the issue promptly.

Can I clear the B257A code myself?

Yes, you can clear the code using an OBDII scanner, but if the underlying issue isnâ€™t resolved, the code is likely to return.

Will resetting the vehicle's computer fix the B257A code?

Resetting the computer may temporarily clear the code, but it won't fix the underlying issue causing the correlation malfunction.

Should I consult a professional if I encounter the B257A code?

If you're not comfortable diagnosing or repairing electrical issues, it's advisable to consult a professional mechanic for a thorough diagnosis and repair.