AutoCodes – GMC – B3889 GMC

B3889 GMC Code - Trailer Brake Lamps

Quick Answer

The brake pedal position sensor is used to sense the action of the driver application of the brake pedal. Common causes include Faulty Trailer Brake Lamps, Trailer Brake Lamps harness is open or shorted, Trailer Brake 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: B3889 GMC indicates Trailer Brake Lamps.
Common causes: Common causes include Faulty Trailer Brake Lamps, Trailer Brake Lamps harness is open or shorted, Trailer Brake 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 508

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 23, 2020

Description
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
FAQs
Comments
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Code B3889 GMC Description

The brake pedal position sensor is used to sense the action of the driver application of the brake pedal. The brake pedal position sensor provides an analog voltage signal that will increase as the brake pedal is applied. The Body Control Module (BCM) provides a low reference signal and a 5 V reference voltage to the brake pedal position sensor. When the variable signal reaches a voltage threshold indicating the brakes have been applied, the BCM applies battery voltage to the center high mounted stop lamp control circuit and Trailer Lighting Control Module. The Trailer Lighting Control Module responds by applying battery voltage to the trailer stop lamp control circuit illuminating the trailer stop lamps.

OBDII Code B3889 GMC - Trailer Brake Lamps - AutoCodes.com — B3889 GMC Code - Trailer Brake Lamps

What does this mean?

What are the Possible Causes of the DTC B3889 GMC?

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

How to Fix the DTC B3889 GMC?

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

B3889 02 Trailer Brake Lamps Circuit Short to Ground
B3889 04 Trailer Brake Lamps Circuit Open

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the B3889 GMC 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 B3889 GMC Code

1. What does OBDII code B3889 GMC indicate?

The code B3889 GMC specifically refers to a fault in the trailer brake lamps circuit.

2. What are the common symptoms of OBDII code B3889 GMC?

Common symptoms include inoperative trailer brake lamps, a warning light on the dashboard, and potential issues with the trailer brake system.

3. What are some possible causes of OBDII code B3889 GMC?

Possible causes of this code may include a faulty trailer brake lamp bulb, damaged wiring, a defective brake lamp switch, or a problem in the trailer brake control module.

4. How can I diagnose the issue related to OBDII code B3889 GMC?

To diagnose the problem, you can start by visually inspecting the trailer brake lamps and their wiring. Using a multimeter to check for continuity and testing the brake lamp switch can also help pinpoint the cause.

5. Can I still drive my vehicle with OBDII code B3889 GMC?

It is not recommended to drive your vehicle with inoperative trailer brake lamps, as this can pose a safety risk, especially when towing a trailer.

6. How can I repair OBDII code B3889 GMC?

Repairing the issue may involve replacing a faulty brake lamp bulb, repairing damaged wiring, replacing the brake lamp switch, or addressing any issues with the trailer brake control module.

7. Do I need a professional mechanic to fix OBDII code B3889 GMC?

While some repairs related to this code can be done by DIY enthusiasts, complex electrical issues may require the expertise of a professional mechanic.

8. How much does it typically cost to repair OBDII code B3889 GMC?

The cost of repair can vary depending on the exact cause of the issue and whether any parts need to be replaced. It is advisable to get a diagnosis from a mechanic for an accurate estimate.

9. Are there any preventive measures to avoid OBDII code B3889 GMC in the future?

Regularly checking and maintaining your trailer brake lamps, as well as inspecting the wiring for any damage, can help prevent issues that trigger this OBDII code.

10. Can OBDII code B3889 GMC affect other vehicle systems?

While this code specifically relates to the trailer brake lamps, addressing the underlying issue promptly is important to ensure the overall safety and functionality of your vehicle's electrical system.