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Engine-Codes – GMC – B1840 2015 GMC Sierra

B1840 2015 GMC Sierra Code - Driver Seat Lumbar Up Switch Circuit

Quick Answer

The B1840 diagnostic trouble code (DTC) for a 2015 GMC Sierra specifically relates to the driver seat lumbar up switch circuit. Common causes include Faulty lumbar support switch, Wiring issues such as shorts or open circuits, Loose or corroded connectors in the circuit. 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
B1840 2015 GMC Sierra indicates Driver Seat Lumbar Up Switch Circuit.
Common causes
Common causes include Faulty lumbar support switch, Wiring issues such as shorts or open circuits, Loose or corroded connectors in the circuit.
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.
What is this?
Table of contents Created and updated by William Orellana on Sep 13, 2024
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Code B1840 2015 GMC Sierra Description

The B1840 diagnostic trouble code (DTC) for a 2015 GMC Sierra specifically relates to the driver seat lumbar up switch circuit. This code indicates that there is a malfunction in the circuit responsible for controlling the lumbar support adjustment in the driver's seat. The lumbar support feature is designed to provide additional lower back support and comfort for the driver, allowing for a more ergonomic seating position during long drives.

OBDII Code B1840 2015 GMC Sierra - Driver Seat Lumbar Up Switch Circuit
B1840 2015 GMC Sierra Code - Driver Seat Lumbar Up Switch Circuit

Common Causes of B1840 2015 GMC Sierra

  1. Faulty lumbar support switch.
  2. Wiring issues such as shorts or open circuits.
  3. Loose or corroded connectors in the circuit.
  4. Damage to the lumbar support motor.
  5. Issues with the control module responsible for the lumbar support adjustment.

Symptoms of B1840 2015 GMC Sierra

  1. Inability to adjust the lumbar support in the driver's seat.
  2. Lumbar support adjustment controls not responding.
  3. Strange noises or clicking sounds when attempting to adjust the lumbar support.
  4. Lumbar support adjustment working intermittently.
  5. Illumination of the airbag warning light on the dashboard (in some cases).

How to Fix B1840 2015 GMC Sierra

  1. Begin by inspecting the lumbar support switch, wiring, and connectors for any visible damage or corrosion. Replace or repair any damaged components.
  2. Test the lumbar support switch using a multimeter to check for continuity and proper functionality. Replace the switch if necessary.
  3. Check the wiring harness for any shorts or open circuits using a wiring diagram and a multimeter. Repair or replace any damaged wiring.
  4. Test the lumbar support motor to ensure it is functioning correctly. Replace the motor if it is faulty.
  5. Clear the DTC using a diagnostic scan tool and test the lumbar support adjustment to confirm that the issue has been resolved.

Cost to Fix B1840 2015 GMC Sierra

The typical repair costs for addressing the B1840 DTC on a 2015 GMC Sierra can vary depending on the specific cause of the issue and the labor rates at the auto repair shop. In general, the cost of parts such as a new lumbar support switch or motor can range from $50 to $200. Labor costs can add an additional $80 to $150 per hour, with the total repair bill likely falling within the $150 to $500 range.

What does this mean?

Tech Notes for B1840 2015 GMC Sierra









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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 B1840 2015 GMC Sierra Code

1. What are the common symptoms of OBDII code B1840 in a 2015 GMC Sierra related to the driver seat lumbar up switch circuit?

The common symptoms include the driver seat lumbar up switch not functioning, inability to adjust the lumbar support, or the switch not responding.

2. What are the possible causes of OBDII code B1840 in a 2015 GMC Sierra?

Potential causes of this code may include a faulty driver seat lumbar up switch, damaged wiring or connectors in the circuit, or a malfunctioning control module.

3. How can I diagnose the issue related to OBDII code B1840 in my 2015 GMC Sierra?

You can start by inspecting the driver seat lumbar up switch for any visible damage, checking the wiring and connectors for loose connections or corrosion, and using a multimeter to test the circuit continuity.

4. Is it safe to continue driving my 2015 GMC Sierra with OBDII code B1840 related to the driver seat lumbar up switch circuit?

It is generally safe to drive the vehicle with this code, but it is recommended to address the issue promptly to ensure proper functioning of the driver seat lumbar support.

5. How can I repair OBDII code B1840 in my 2015 GMC Sierra myself?

You can attempt to repair this code by replacing the faulty driver seat lumbar up switch, repairing any damaged wiring or connectors, or resetting the control module after fixing the issue.

6. Can resetting the control module help clear OBDII code B1840 in my 2015 GMC Sierra?

Resetting the control module may help clear the code temporarily, but it is important to address the root cause of the issue to prevent the code from reoccurring.

7. Are there any common mistakes to avoid when troubleshooting OBDII code B1840 in a 2015 GMC Sierra?

Avoid overlooking simple issues like loose connections or blown fuses, as these can often be the cause of the problem related to the driver seat lumbar up switch circuit.

8. Should I seek professional help to diagnose and repair OBDII code B1840 in my 2015 GMC Sierra?

If you are unsure about diagnosing or repairing the issue yourself, it is recommended to seek the assistance of a qualified mechanic or dealership to properly address the problem.

9. How much can I expect to pay for repairing OBDII code B1840 in my 2015 GMC Sierra at a professional service center?

The cost of repairing this code can vary depending on the exact cause of the issue, but you can expect to pay for parts, labor, and diagnostic fees at a professional service center.

10. Is the driver seat lumbar up switch circuit covered under any warranty for a 2015 GMC Sierra?

Depending on the warranty coverage of your vehicle, the driver seat lumbar up switch circuit may be covered under a powertrain or extended warranty, so it is advisable to check with your dealership for more information.

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