AutoCodes – GMC – B3949 2015 GMC Sierra

B3949 2015 GMC Sierra Code - Right Front Turn Signal Circuit

Quick Answer

Ground is applied at all times to the turn signal/multifunction switch. Common causes include Faulty Right Front Turn Signal Lamp, Right Front Turn Signal Lamp harness is open or shorted, Right Front Turn Signal Lamp 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: B3949 2015 GMC Sierra indicates Right Front Turn Signal Circuit.
Common causes: Common causes include Faulty Right Front Turn Signal Lamp, Right Front Turn Signal Lamp harness is open or shorted, Right Front Turn Signal Lamp 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 172

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 Jun 17, 2023

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code B3949 2015 GMC Sierra Description

Ground is applied at all times to the turn signal/multifunction switch. The turn signal lamps may only be activated with the ignition switch in the ON or START positions. When the turn signal/multifunction switch is placed in either the TURN RIGHT or TURN LEFT position, ground is applied to the Body Control Module (BCM) through either the right turn or left turn signal switch signal circuit. The BCM responds to the turn signal switch input by applying a pulsating voltage to the front and rear turn signal lamps through there respective control circuits. When a turn signal request is received by the BCM, a serial data message is sent to the instrument cluster requesting the respective turn signal indicator be pulsed ON and OFF. The Diagnostic Trouble Code (DTC) will be set when the BCM detects an open/high resistance in the left front turn signal control circuit.

OBDII Code B3949 2015 GMC Sierra - Right Front Turn Signal Circuit - AutoCodes.com — B3949 2015 GMC Sierra Code - Right Front Turn Signal Circuit

What does this mean?

What are the Possible Causes of the DTC B3949 2015 GMC Sierra?

Faulty Right Front Turn Signal Lamp
Right Front Turn Signal Lamp harness is open or shorted
Right Front Turn Signal Lamp circuit poor electrical connection
Faulty Body Control Module (BCM)

How to Fix the DTC B3949 2015 GMC Sierra?

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 is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the B3949 2015 GMC Sierra 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.

Need more information about the B3949 2015 GMC Sierra code?

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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 B3949 2015 GMC Sierra Code

1. What does the OBDII code B3949 mean on a 2015 GMC Sierra?

B3949 indicates an issue with the right front turn signal circuit, often related to a wiring, bulb, or module malfunction.

2. What are the symptoms of code B3949 in a 2015 GMC Sierra?

Symptoms include the right front turn signal not working, hyper-flashing, or a dashboard warning about the turn signal system.

3. What causes the B3949 code to appear?

Common causes include a burnt-out turn signal bulb, damaged wiring, a faulty connector, or a malfunctioning body control module (BCM).

4. Can a faulty bulb cause the B3949 code?

Yes, a burnt-out or improperly installed bulb is a common cause of this code.

5. How do I fix the B3949 code on my 2015 GMC Sierra?

Start by checking and replacing the right front turn signal bulb, inspecting the wiring and connectors, and testing the BCM if necessary.

6. How do I diagnose the B3949 code?

Use a diagnostic scanner to confirm the code, visually inspect the bulb and wiring, and test the circuit for continuity and proper voltage.

7. Can a damaged wiring harness cause the B3949 code?

Yes, a damaged or corroded wiring harness can disrupt the turn signal circuit and trigger this code.

8. Is it safe to drive with the B3949 code on my GMC Sierra?

While the vehicle is drivable, a malfunctioning turn signal can create a safety hazard by reducing visibility to other drivers.

9. Can the body control module (BCM) be the problem for code B3949?

Yes, if the bulb and wiring are in good condition, the BCM could be faulty and may need reprogramming or replacement.

10. Will clearing the code fix the B3949 issue permanently?

Clearing the code without addressing the root cause will likely result in the code returning. Proper diagnosis and repair are necessary.

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