AutoCodes – Buick – B3890 Buick

B3890 Buick Code - Trailer Backup Lamps Circuit

Quick Answer

The Trailer Lighting Control Module receives a serial data message from the Body Control Module (BCM) indicating that the vehicle backup lamps have been activated. Common causes include Faulty Trailer Backup Lamps, Trailer Backup Lamps harness is open or shorted, Trailer Backup Lamps 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: B3890 Buick indicates Trailer Backup Lamps Circuit.
Common causes: Common causes include Faulty Trailer Backup Lamps, Trailer Backup Lamps harness is open or shorted, Trailer Backup Lamps 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 470

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 Mar 24, 2020

Description
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
FAQs
Comments
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Code B3890 Buick Description

The Trailer Lighting Control Module receives a serial data message from the Body Control Module (BCM) indicating that the vehicle backup lamps have been activated. The Trailer Lighting Control Module responds by applying battery voltage to the trailer backup lamp control circuit illuminating the trailer backup lamps. The Diagnostic Trouble Code (DTC) sets when the Trailer Lighting Control Module detects a short to ground or an open/high resistance in the trailer backup lamps control circuit.

OBDII Code B3890 Buick - Trailer Backup Lamps Circuit - AutoCodes.com — B3890 Buick Code - Trailer Backup Lamps Circuit

What does this mean?

What are the Possible Causes of the DTC B3890 Buick?

Faulty Trailer Backup Lamps
Trailer Backup Lamps harness is open or shorted
Trailer Backup Lamps circuit poor electrical connection
Faulty Trailer Lighting Control Module

How to Fix the DTC B3890 Buick?

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 does this mean?

Code Tech Notes

B3890 02 Trailer Backup Lamps Circuit Short to Ground
B3890 04 Trailer Backup Lamps Circuit Open

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the B3890 Buick 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 B3890 Buick Code

1. What does the OBDII code B3890 mean on a Buick?

The B3890 code indicates a problem in the trailer backup lamps circuit, which may involve issues with wiring, connectors, or the control module.

2. What are the common symptoms of the B3890 code?

The most common symptoms include trailer backup lamps not working, a warning light on the dashboard, or a stored trouble code in the system.

3. What causes the B3890 code on a Buick?

The code is typically caused by damaged wiring, corroded or loose connectors, a malfunctioning trailer lamp, or a faulty control module.

4. How can I diagnose the B3890 code?

Start by inspecting the trailer lamp wiring and connectors for damage or corrosion. Use a multimeter to check for continuity and proper voltage in the circuit.

5. Can I still drive my Buick with the B3890 code active?

Yes, you can drive the vehicle, but trailer backup lamps may not function, which could be problematic if towing a trailer at night or in low visibility conditions.

6. How do I fix the B3890 code on my Buick?

Repairs may include replacing damaged wiring, cleaning or reconnecting corroded connectors, or replacing a faulty trailer lamp or control module.

7. How much does it cost to repair the B3890 code?

Repair costs can range from $50 to $300 or more, depending on whether the issue is a simple wiring fix or requires replacing a component like the control module.

8. Can a blown fuse cause the B3890 code?

Yes, a blown fuse in the trailer backup lamp circuit can trigger the B3890 code. Check and replace any blown fuses as needed.

9. Do I need a mechanic to fix the B3890 code?

While basic wiring or fuse issues can be resolved by most DIYers, complex problems like a faulty control module may require professional diagnosis and repair.

10. Will clearing the B3890 code solve the problem?

Clearing the code without fixing the underlying issue will only temporarily remove the error. The code will likely return if the problem is not addressed.