AutoCodes – Cadillac – B1840 Cadillac

B1840 Cadillac Code - Driver Seat Lumbar Up Switch Circuit

Quick Answer

The Seat Memory Control Module supplies a reference voltage to each signal circuit of the Driver Seat Adjuster Switch. Common causes include Faulty Driver Seat Adjuster Switch, Driver Seat Adjuster Switch harness is open or shorted, Driver Seat Adjuster 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: B1840 Cadillac indicates Driver Seat Lumbar Up Switch Circuit.
Common causes: Common causes include Faulty Driver Seat Adjuster Switch, Driver Seat Adjuster Switch harness is open or shorted, Driver Seat Adjuster 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 287

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 Apr 24, 2023

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code B1840 Cadillac Description

The Seat Memory Control Module supplies a reference voltage to each signal circuit of the Driver Seat Adjuster Switch. When the power seat or lumbar switches are pressed, the appropriate signal circuit from the Seat Memory Control Module is pulled low through the switch contacts indicating the power seat command. The Seat Memory Control Module then commands the driver seat or lumbar to move in response to the switch signals. The Diagnostic Trouble Code (DTC) will be set when there is a short to ground on a switch signal circuit.

OBDII Code B1840 Cadillac - Driver Seat Lumbar Up Switch Circuit - AutoCodes.com — B1840 Cadillac Code - Driver Seat Lumbar Up Switch Circuit

What does this mean?

What are the Possible Causes of the DTC B1840 Cadillac?

Faulty Driver Seat Adjuster Switch
Driver Seat Adjuster Switch harness is open or shorted
Driver Seat Adjuster Switch circuit poor electrical connection
Faulty Seat Memory Control Module

How to Fix the DTC B1840 Cadillac?

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 B1840 Cadillac 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.

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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 Cadillac Code

1. What does the OBDII code B1840 mean on a Cadillac?

The B1840 code indicates an issue with the driver seat lumbar up switch circuit, often caused by a fault in the wiring, switch, or motor.

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

Common symptoms include the driver seat lumbar support not moving up, the lumbar adjustment switch being unresponsive, or intermittent operation.

3. What causes the B1840 code to appear?

This code is typically caused by a faulty lumbar up switch, damaged wiring or connectors in the circuit, or a malfunctioning lumbar motor.

4. Can I still drive my Cadillac with a B1840 code?

Yes, the B1840 code does not affect the drivability of the vehicle but may impact the comfort and adjustability of the driver's seat.

5. How do I troubleshoot a B1840 code?

Start by inspecting the lumbar up switch, checking for loose or damaged wiring, and testing the lumbar motor for proper operation.

6. Does the lumbar motor need to be replaced if I get a B1840 code?

Not necessarily. The issue could be with the switch or wiring. Test the motor first to confirm if it is the source of the problem.

7. How much does it cost to fix a B1840 code?

Repair costs can vary, but replacing the lumbar switch may cost $50â€“$150, while lumbar motor replacement could range from $200â€“$500, depending on labor and parts.

8. Can I fix the B1840 code myself?

If you are familiar with automotive electrical systems, you can inspect and replace the switch or repair wiring. Otherwise, itâ€™s best to consult a professional.

9. Is the B1840 code specific to Cadillacs?

While the code itself is used industry-wide, its meaning and application to the lumbar up switch circuit are specific to Cadillac and similar GM vehicles.

10. How do I clear the B1840 code after repairs?

After fixing the issue, you can clear the code using an OBDII scanner. If the problem is resolved, the code should not return.