AutoCodes – GMC – B256B GMC

B256B GMC 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 GMC 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 291

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

What does this mean?

What are the Possible Causes of the DTC B256B GMC?

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 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 B256B 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 B256B GMC code?

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Need Help with the Code?

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Information for Specific GMC Models

B256B 2014 GMC Sierra — Cargo Lamps Switch Circuit Malfunction
B256B 2015 GMC Sierra — Cargo Lamps Switch Circuit Malfunction
B256B 2016 GMC Sierra — Cargo Lamps Switch Circuit Malfunction
B256B 2017 GMC Sierra — Cargo Lamps Switch Circuit Malfunction
B256B 2018 GMC Sierra — Cargo Lamps Switch 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 B256B GMC Code

1. What are the common symptoms of OBDII code B256B GMC (Cargo Lamps Switch Circuit Malfunction)?

- Common symptoms include non-functioning cargo lamps, flickering or dimming cargo lamps, and illuminated dashboard warning lights.

2. What are the possible causes of OBDII code B256B GMC?

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

3. How can I diagnose the OBDII code B256B GMC issue?

- Diagnose the issue by visually inspecting the cargo lamp switch and circuit for any visible damage, checking the wiring and connectors for continuity, and using a diagnostic scanner to retrieve fault codes.

4. Can I still drive my vehicle with the OBDII code B256B GMC active?

- It is generally safe to drive the vehicle with this code, but it is recommended to address the issue promptly to avoid potential safety hazards and further damage.

5. How can I repair the Cargo Lamps Switch Circuit Malfunction?

- Repair options include replacing the cargo lamp switch, repairing or replacing damaged wiring or connectors, and reprogramming or replacing the control module if necessary.

6. Will resetting the OBDII code B256B GMC make it go away permanently?

- Resetting the code may temporarily clear the warning light, but if the underlying issue is not fixed, the code is likely to reappear after some driving cycles.

7. Can weather conditions affect the occurrence of OBDII code B256B GMC?

- Extreme weather conditions, such as exposure to moisture or extreme heat, can potentially damage the cargo lamp circuit components and contribute to the malfunction.

8. Is it possible to prevent OBDII code B256B GMC from occurring in the future?

- Regular maintenance checks, timely repair of any electrical issues, and using high-quality replacement parts can help prevent the recurrence of this OBDII code.

9. How long does it typically take to repair OBDII code B256B GMC?

- The repair time can vary depending on the exact cause of the malfunction, but it may take anywhere from 1 to 3 hours to diagnose and fix the Cargo Lamps Switch Circuit issue.

10. Can a DIY enthusiast fix OBDII code B256B GMC at home?

- DIY enthusiasts with intermediate automotive repair skills and access to proper tools can attempt to diagnose and fix the Cargo Lamps Switch Circuit Malfunction, but professional help may be needed for complex issues.