AutoCodes – GMC – B3887 GMC

B3887 GMC Code - Trailer Left Turn Signal Circuit

Quick Answer

The Trailer Lighting Control Module receives a serial data message from the Body Control Module (BCM) indicating that the vehicle left or right turn signal lamp has been activated. Common causes include Faulty Trailer Left Turn Signal, Trailer Left Turn Signal harness is open or shorted, Trailer Left Turn Signal 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: B3887 GMC indicates Trailer Left Turn Signal Circuit.
Common causes: Common causes include Faulty Trailer Left Turn Signal, Trailer Left Turn Signal harness is open or shorted, Trailer Left Turn Signal 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 474

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 B3887 GMC Description

The Trailer Lighting Control Module receives a serial data message from the Body Control Module (BCM) indicating that the vehicle left or right turn signal lamp has been activated. The Trailer Lighting Control Module responds by applying a pulsating voltage to the appropriate trailer turn signal lamp through their respective control circuit illuminating the desired trailer turn signal lamp. The Diagnostic Trouble Code (DTC) sets when the Trailer Lighting Control Module detects a short to ground or an open/high resistance in the left trailer turn signal control circuit.

OBDII Code B3887 GMC - Trailer Left Turn Signal Circuit - AutoCodes.com — B3887 GMC Code - Trailer Left Turn Signal Circuit

What does this mean?

What are the Possible Causes of the DTC B3887 GMC?

Faulty Trailer Left Turn Signal
Trailer Left Turn Signal harness is open or shorted
Trailer Left Turn Signal circuit poor electrical connection
Faulty Trailer Lighting Control Module

How to Fix the DTC B3887 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

B3887 02 Trailer Left Turn Signal Circuit Short to Ground
B3887 04 Trailer Left Turn Signal Circuit Open

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the B3887 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 B3887 GMC Code

What does the OBDII code B3887 indicate for a GMC vehicle?

The B3887 code indicates a malfunction in the trailer left turn signal circuit, often related to issues with the trailer wiring or the vehicleâ€™s tow package.

What are the common symptoms associated with the B3887 code?

Common symptoms include a malfunctioning left turn signal on the trailer, warning lights on the dashboard, or a message indicating a trailer fault.

What are potential causes of the B3887 code?

Potential causes include damaged wiring in the trailer harness, a faulty trailer connector, a blown fuse, or problems with the vehicleâ€™s body control module.

How can I diagnose the B3887 code effectively?

To diagnose, check the trailer connector for corrosion or damage, inspect the wiring harness for breaks, and test the left turn signal circuit for continuity.

What should I do if my trailerâ€™s left turn signal isnâ€™t working?

First, check the trailer's bulb and wiring. If they are fine, inspect the vehicle's trailer connector and wiring for issues, and consider testing the vehicleâ€™s turn signal system.

Are there any common fixes for the B3887 code?

Common fixes include repairing or replacing damaged wiring, cleaning or replacing the trailer connector, and ensuring all connections are secure and corrosion-free.

Can I drive my GMC if the B3887 code is active?

While you can drive the vehicle, itâ€™s advisable to fix the issue to ensure safe towing and compliance with traffic regulations regarding trailers.

Will clearing the B3887 code fix the issue permanently?

Clearing the code may reset the warning temporarily, but if the underlying issue isnâ€™t resolved, the code will likely reappear.

Is it safe to tow a trailer with a B3887 code present?

Towing with this code active may not be safe, as the left turn signal on the trailer may not function properly, increasing the risk of accidents.

Can a malfunctioning body control module cause the B3887 code?

Yes, a faulty body control module can affect the trailer signal circuits, leading to the B3887 code being triggered if it fails to communicate correctly.