AutoCodes – GMC – B256B 2018 GMC Sierra

B256B 2018 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 2018 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 236

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 2018 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 2018 GMC Sierra - Cargo Lamps Switch Circuit Malfunction - AutoCodes.com — B256B 2018 GMC Sierra Code - Cargo Lamps Switch Circuit Malfunction

What does this mean?

What are the Possible Causes of the DTC B256B 2018 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 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 B256B 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 B256B 2018 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 2018 GMC Sierra Code

1. What are the common symptoms of OBDII code B256B in a 2018 GMC Sierra related to the Cargo Lamps Switch Circuit Malfunction?

- Common symptoms include non-functional cargo lamps, flickering lights, or the cargo lamp staying on or off when it shouldn't.

2. What are the possible causes of the Cargo Lamps Switch Circuit Malfunction code B256B in a 2018 GMC Sierra?

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

3. How can I diagnose the Cargo Lamps Switch Circuit Malfunction code B256B in my 2018 GMC Sierra?

- Diagnosis involves visually inspecting the wiring and connectors, testing the cargo lamp switch for proper operation, and using a scan tool to check for stored fault codes.

4. Can a DIY enthusiast repair the Cargo Lamps Switch Circuit Malfunction code B256B in a 2018 GMC Sierra?

- Yes, DIY repairs can include replacing the cargo lamp switch, repairing damaged wiring, or addressing faulty connectors if the issue is identified correctly.

5. Is it safe to continue driving a 2018 GMC Sierra with the Cargo Lamps Switch Circuit Malfunction code B256B?

- It is generally safe to drive with this code, but it's advisable to address the issue promptly to ensure the proper functioning of the cargo lamps.

6. How much does it typically cost to repair the Cargo Lamps Switch Circuit Malfunction code B256B in a 2018 GMC Sierra?

- The cost can vary depending on the exact cause of the issue, but repairs for this code usually range from $100 to $300, including parts and labor.

7. Are there any troubleshooting tips for resolving the Cargo Lamps Switch Circuit Malfunction code B256B in a 2018 GMC Sierra?

- Troubleshooting tips include checking the cargo lamp fuse, ensuring the cargo lamp bulbs are in good condition, and testing the cargo lamp switch with a multimeter.

8. Can weather conditions or vehicle usage affect the occurrence of the Cargo Lamps Switch Circuit Malfunction code B256B in a 2018 GMC Sierra?

- Yes, extreme weather conditions or frequent usage of the cargo lamps can contribute to the wear and tear of the circuit components, leading to potential malfunctions.

9. How long does it typically take a mechanic to repair the Cargo Lamps Switch Circuit Malfunction code B256B in a 2018 GMC Sierra?

- The repair time can vary based on the exact issue, but a skilled mechanic can usually diagnose and fix this problem within 1-2 hours.

10. Are there any recalls or technical service bulletins related to the Cargo Lamps Switch Circuit Malfunction code B256B in a 2018 GMC Sierra?

- It's recommended to check with a GMC dealership or the manufacturer's website to see if there are any relevant recalls or bulletins addressing this specific OBDII code.