Engine-Codes.com
Engine-Codes – Generic – B3890

B3890 Code - Trailer Backup Lamps Circuit

Quick Answer

The B3890 code indicates a problem with the trailer backup lamps circuit in the vehicle. Common causes include Faulty wiring or connectors in the backup lamps circuit, Burned out backup lamp bulbs, Malfunctioning backup lamp switch. 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 indicates Trailer Backup Lamps Circuit.
Common causes
Common causes include Faulty wiring or connectors in the backup lamps circuit, Burned out backup lamp bulbs, Malfunctioning backup lamp switch.
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 Aug 19, 2024
💬 Need more help? Ask Auto Expert for instant answers — it's free!
AutoCodes App

Fix Your Car Smarter

Try the New AutoCodes App!

Get complete OBDII diagnostics, repair solutions, and cost estimates, plus AI chat support on demand.

AutoCodes App on Google Play

Code B3890 Description

The B3890 code indicates a problem with the trailer backup lamps circuit in the vehicle. This code is usually triggered when there is a malfunction in the wiring, connectors, or components related to the backup lamps that are used when towing a trailer. The backup lamps are essential for providing visibility when reversing the vehicle, especially when towing a trailer or camper. If this circuit is not functioning correctly, it can compromise the safety of the driver and others on the road.

OBDII Code B3890 - Trailer Backup Lamps Circuit
B3890 Code - Trailer Backup Lamps Circuit

Common Causes of B3890

  1. Faulty wiring or connectors in the backup lamps circuit.
  2. Burned out backup lamp bulbs.
  3. Malfunctioning backup lamp switch.
  4. Corrosion in the wiring harness.
  5. Issues with the body control module.

Symptoms of B3890

  1. Backup lamps not turning on when the vehicle is in reverse.
  2. Dim or flickering backup lamps.
  3. Backup lamps staying on continuously.
  4. Fuse blowing repeatedly.
  5. Dashboard warning light illuminated.

How to Fix B3890

  1. Begin by inspecting the wiring and connectors in the backup lamps circuit for any damage or corrosion. Repair or replace any faulty components.
  2. Check and replace any burned out backup lamp bulbs.
  3. Test the backup lamp switch and replace if necessary.
  4. Inspect the body control module for any issues and reprogram or replace as needed.
  5. Clear the diagnostic trouble codes and test the backup lamps to ensure they are functioning properly.

Cost to Fix B3890

The typical repair costs for resolving the B3890 code related to the trailer backup lamps circuit can range from $100 to $300, depending on the specific cause of the issue and the cost of parts and labor. It's important to note that diagnostic time and labor rates at auto repair shops can vary, so it's advisable to check with local shops for a more accurate estimate.

What does this mean?

Tech Notes for B3890

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

Need more information about the B3890 code?

Need more information on how to fix the B3890 code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the B3890 code diagnosed by a professional: Find a repair shop in your area

Code B3890 Information for Specific Makes

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 Code

1. What does OBDII code B3890 mean?

B3890 indicates an issue with the Trailer Backup Lamps Circuit, which controls the backup lights on a trailer connected to the vehicle.

2. What are the common symptoms of code B3890?

Symptoms include trailer backup lamps not illuminating, a warning light on the dashboard, or a stored diagnostic trouble code.

3. What causes the B3890 code to appear?

Common causes include a damaged or corroded trailer wiring harness, a faulty trailer lamp, a blown fuse, or an issue with the vehicle's body control module (BCM).

4. Can a bad connection trigger code B3890?

Yes, a loose or poor connection in the trailer wiring harness or connector can trigger this code.

5. How do you diagnose the B3890 code?

Start by inspecting the trailer wiring and backup lamp connections for damage or corrosion, check the fuse related to the trailer lamps, and use a diagnostic scanner to confirm the code.

6. Is it safe to drive with the B3890 code?

Yes, it’s generally safe to drive, but the trailer backup lamps may not function, which can be a safety concern when reversing.

7. How do you fix the B3890 code?

Repairs may involve replacing damaged wiring, cleaning corroded connectors, replacing a blown fuse, or reprogramming the BCM if necessary.

8. Can a trailer lamp failure cause the B3890 code?

Yes, a burned-out or faulty trailer lamp can disrupt the circuit and trigger this code.

9. Do I need to replace the BCM if I get code B3890?

Not usually. The BCM is rarely the root cause; check the wiring, fuses, and lamps first before considering BCM replacement.

10. How can I prevent the B3890 code from occurring?

Regularly inspect and maintain the trailer wiring harness and connectors, and ensure the backup lamps on the trailer are functioning properly.

Discuss the causes and fixes for B3890 OBDII Code

Submit a New Comment

Code B3890 comments

No comments found for this page.