AutoCodes – GMC – B256B 2017 GMC Sierra

B256B 2017 GMC Sierra Code - Cargo Lamps Switch Circuit Malfunction

Quick Answer

The cargo lamp relay is always supplied with battery voltage. Common causes include Faulty Cargo Lamps Switch, Cargo Lamps Switch harness is open or shorted, Cargo Lamps 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: B256B 2017 GMC Sierra indicates Cargo Lamps Switch Circuit Malfunction.
Common causes: Common causes include Faulty Cargo Lamps Switch, Cargo Lamps Switch harness is open or shorted, Cargo Lamps 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 171

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 B256B 2017 GMC Sierra Description

The cargo lamp relay is always supplied with battery voltage. The cargo lamp switch signal circuit is grounded momentarily by pressing the cargo lamp switch. The Body Control Module (BCM) energizes the cargo lamp relay by applying ground to the cargo lamp relay control circuit. When the cargo lamp relay is energized, the relay switch contacts close, and battery voltage is applied through the F9DR fuse to the cargo lamp control circuit which illuminates the cargo lamps. The Diagnostic Trouble Code (DTC) will be set when the BCM detects a short to ground in the cargo lamp switch signal circuit.

OBDII Code B256B 2017 GMC Sierra - Cargo Lamps Switch Circuit Malfunction - AutoCodes.com — B256B 2017 GMC Sierra Code - Cargo Lamps Switch Circuit Malfunction

What does this mean?

What are the Possible Causes of the DTC B256B 2017 GMC Sierra?

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

How to Fix the DTC B256B 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 B256B 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 B256B 2017 GMC Sierra code?

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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 B256B 2017 GMC Sierra Code

1. What are the common symptoms of OBDII code B256B in a 2017 GMC Sierra related to the Cargo Lamps Switch Circuit Malfunction?

The common symptoms include inoperative cargo lamps, flickering or dim cargo lamps, or the cargo lamp switch not functioning properly.

2. What are the possible causes of the Cargo Lamps Switch Circuit Malfunction code B256B in a 2017 GMC Sierra?

Potential causes include a faulty cargo lamp switch, damaged wiring or connectors in the cargo lamp circuit, or a malfunctioning cargo lamp control module.

3. How can I diagnose the Cargo Lamps Switch Circuit Malfunction in my 2017 GMC Sierra?

You can start by checking the cargo lamp switch for proper functionality, inspecting the wiring and connectors for any damage, and using a diagnostic scan tool to read the B256B trouble code.

4. Can a DIY enthusiast repair OBDII code B256B related to the Cargo Lamps Switch Circuit Malfunction in a 2017 GMC Sierra?

If you have experience working with automotive electrical systems, you may be able to repair this issue by replacing the faulty cargo lamp switch, repairing damaged wiring, or addressing any issues with the cargo lamp control module.

5. Is it important to address the Cargo Lamps Switch Circuit Malfunction code B256B in a 2017 GMC Sierra promptly?

Yes, it is essential to address this issue promptly to ensure the proper functioning of the cargo lamps, which are crucial for visibility and safety, especially when loading or unloading cargo at night.

6. Can extreme weather conditions contribute to triggering the Cargo Lamps Switch Circuit Malfunction code B256B in a 2017 GMC Sierra?

Extreme weather conditions such as moisture, heat, or cold can potentially cause electrical issues in the cargo lamp circuit, leading to the triggering of the B256B trouble code.

7. What tools may be necessary for repairing the Cargo Lamps Switch Circuit Malfunction in a 2017 GMC Sierra?

Tools such as a multimeter for testing electrical connections, a diagnostic scan tool for reading and clearing trouble codes, and basic hand tools for removing components like the cargo lamp switch may be necessary for the repair.

8. Are there any recalls or technical service bulletins related to the Cargo Lamps Switch Circuit Malfunction code B256B in a 2017 GMC Sierra?

It's advisable to check with a GMC dealership or the manufacturer's website to see if there are any recalls or technical service bulletins related to the B256B trouble code in the 2017 Sierra model.

9. Can a loose cargo lamp bulb cause the B256B trouble code in a 2017 GMC Sierra?

While a loose cargo lamp bulb may not directly trigger the B256B code, it's still important to ensure all components in the cargo lamp circuit are in good working condition to prevent any potential issues.

10. How much can I expect to pay for professional repair of the Cargo Lamps Switch Circuit Malfunction in a 2017 GMC Sierra?

The cost of professional repair for the B256B trouble code can vary depending on the specific cause of the issue, but it's recommended to consult with a trusted mechanic or dealership for an accurate estimate.