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B1840 2017 GMC Sierra Code - Driver Seat Lumbar Up Switch Circuit

Quick Answer

The B1840 diagnostic trouble code for a 2017 GMC Sierra specifically points to an issue with the driver seat lumbar up switch circuit. Common causes include Faulty lumbar support switch, Damaged or frayed wiring in the lumbar support circuit, Failed lumbar support control module. 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 2017 GMC Sierra indicates Driver Seat Lumbar Up Switch Circuit.
Common causes
Common causes include Faulty lumbar support switch, Damaged or frayed wiring in the lumbar support circuit, Failed lumbar support control module.
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 10, 2024
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Code B1840 2017 GMC Sierra Description

The B1840 diagnostic trouble code for a 2017 GMC Sierra specifically points to an issue with 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 to the driver, and when this circuit fails, it can lead to an inability to adjust the lumbar support or potential issues with the seat's overall comfort and ergonomics.

OBDII Code B1840 2017 GMC Sierra - Driver Seat Lumbar Up Switch Circuit
B1840 2017 GMC Sierra Code - Driver Seat Lumbar Up Switch Circuit

Common Causes of B1840 2017 GMC Sierra

  1. Faulty lumbar support switch.
  2. Damaged or frayed wiring in the lumbar support circuit.
  3. Failed lumbar support control module.
  4. Loose or corroded electrical connections in the circuit.
  5. Water damage or exposure causing a short in the circuit.

Symptoms of B1840 2017 GMC Sierra

  1. Inability to adjust the driver seat lumbar support.
  2. Unresponsive or erratic behavior from the lumbar support switch.
  3. Lumbar support adjustment only working intermittently.
  4. Strange noises coming from the seat when attempting to adjust the lumbar support.
  5. Illumination of the airbag warning light on the dashboard.

How to Fix B1840 2017 GMC Sierra

  1. Begin by conducting a visual inspection of the lumbar support switch, wiring, and connections to identify any visible damage or issues.
  2. Use a multimeter to test the continuity of the wiring in the lumbar support circuit and check for any shorts or open circuits.
  3. Test the functionality of the lumbar support switch by checking for proper voltage and resistance when activated.
  4. If necessary, replace the faulty lumbar support switch, repair or replace damaged wiring, or address any loose connections in the circuit.
  5. Clear the diagnostic trouble code from the vehicle's system using a diagnostic scanner to ensure the issue has been resolved.

Cost to Fix B1840 2017 GMC Sierra

The typical repair costs for addressing the B1840 code on a 2017 GMC Sierra can vary depending on the specific cause of the issue and the labor rates in your area. On average, the cost of parts for this repair could range from $50 to $200, with additional labor costs ranging from $100 to $300. It's important to consider that diagnosis time and labor rates at auto repair shops can vary significantly, so it's advisable to contact local shops for a more accurate estimate based on your location and vehicle specifics.

What does this mean?

Tech Notes for B1840 2017 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 2017 GMC Sierra Code

1. What does the OBDII code B1840 mean on a 2017 GMC Sierra?

The B1840 code indicates an issue in the driver seat lumbar up switch circuit, which affects the lumbar support adjustment functionality.

2. What are the common symptoms of code B1840 in a GMC Sierra?

Symptoms include the driver seat lumbar support not moving upward, intermittent or unresponsive lumbar controls, or erratic lumbar adjustment behavior.

3. What causes the B1840 code to appear?

Common causes include a faulty lumbar up switch, damaged wiring or connectors in the circuit, or a malfunctioning seat control module.

4. How is the B1840 code diagnosed?

Diagnosis involves inspecting the lumbar switch, checking the wiring and connectors for damage or corrosion, and testing the seat control module for proper operation.

5. Can I still drive my GMC Sierra with the B1840 code?

Yes, the vehicle is still drivable, but the driver seat lumbar support adjustment may not function properly, potentially affecting comfort.

6. How do you fix the B1840 code on a 2017 GMC Sierra?

Repairs can include replacing the lumbar up switch, repairing damaged wiring or connectors, or reprogramming or replacing the seat control module if needed.

7. How much does it cost to repair the B1840 code issue?

The repair cost varies but may range from $50 to $300 depending on whether only the switch or wiring needs repair or if the seat control module requires replacement.

8. Can a blown fuse cause the B1840 code in a GMC Sierra?

While unlikely, a blown fuse for the seat adjustment system could contribute to the problem and should be checked during diagnostics.

9. Is resetting the code enough to fix the B1840 issue?

Resetting the code may clear it temporarily, but the underlying issue must be fixed to prevent the code from returning.

10. Can the B1840 code be caused by normal wear and tear?

Yes, over time, the lumbar adjustment switch or wiring may wear out or become faulty, leading to this code.

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