B3890 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 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.
Code B3890 Description
What are the Possible Causes of the DTC B3890?
- 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?
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.
Code Tech Notes
B3890 04 Trailer Backup Lamps Circuit Open
What is the Cost to Diagnose the Code?
Labor: 1.0
To diagnose the B3890 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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Information for Specific Makes
- B3890 Buick — Trailer Backup Lamps Circuit
- B3890 Cadillac — Trailer Backup Lamps Circuit
- B3890 Chevrolet — Trailer Backup Lamps Circuit
- B3890 GMC — Trailer Backup Lamps Circuit
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
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