AutoCodes – GMC – B257A GMC

B257A GMC 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 GMC 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 799

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

What does this mean?

What are the Possible Causes of the DTC B257A GMC?

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 GMC?

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 GMC 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 GMC code?

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Need Help with the Code?

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Information for Specific GMC Models

B257A 2014 GMC Sierra — Headlamp Switch Input Signals Correlation Malfunction
B257A 2015 GMC Sierra — Headlamp Switch Input Signals Correlation Malfunction
B257A 2016 GMC Sierra — Headlamp Switch Input Signals Correlation Malfunction
B257A 2017 GMC Sierra — Headlamp Switch Input Signals Correlation Malfunction
B257A 2018 GMC Sierra — Headlamp Switch Input Signals Correlation 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 B257A GMC Code

1. What are common symptoms of OBDII code B257A GMC (Headlamp Switch Input Signals Correlation Malfunction)?

- Common symptoms include issues with the headlamp switch functionality, erratic behavior of the vehicle's lighting system, and possible flickering or dimming of the headlights.

2. What are the possible causes of OBDII code B257A GMC?

- The code may be triggered by a faulty headlamp switch, damaged wiring or connectors related to the switch, or a malfunction in the lighting control module.

3. How can I diagnose the cause of OBDII code B257A GMC?

- Diagnosis typically involves inspecting the headlamp switch, checking for any visible damage to wiring or connectors, and using a diagnostic scan tool to analyze the input signals from the switch.

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

- It is generally not recommended to drive with this code present, as it can affect the proper functioning of the lighting system, potentially compromising safety.

5. How can I repair OBDII code B257A GMC?

- Repair options may include replacing the headlamp switch, repairing or replacing damaged wiring or connectors, or reprogramming the lighting control module as needed.

6. Is it possible to reset OBDII code B257A GMC without fixing the underlying issue?

- While clearing the code temporarily may be possible, it is important to address the root cause to prevent the code from reoccurring and ensure proper vehicle functionality.

7. Can extreme weather conditions trigger OBDII code B257A GMC?

- Yes, extreme weather conditions such as water exposure or extreme temperatures can potentially cause electrical components like the headlamp switch to malfunction, leading to the code being triggered.

8. Are there any recalls or technical service bulletins related to OBDII code B257A GMC?

- It is recommended to check with a GMC dealership or manufacturer for any relevant recalls or technical service bulletins related to this specific OBDII code.

9. How long does it typically take to repair OBDII code B257A GMC?

- The repair time can vary depending on the exact cause of the code and the complexity of the repair needed, but it may range from a few hours to a full day in some cases.

10. Can a DIY enthusiast fix OBDII code B257A GMC, or is it best left to professionals?

- While some basic troubleshooting and repairs may be possible for DIY enthusiasts, diagnosing and repairing electrical issues like this code may be best left to experienced professionals to ensure proper resolution.