AutoCodes – GMC – B3949 2018 GMC Sierra

B3949 2018 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 2018 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 328

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 2018 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 2018 GMC Sierra - Right Front Turn Signal Circuit - AutoCodes.com — B3949 2018 GMC Sierra Code - Right Front Turn Signal Circuit

What does this mean?

What are the Possible Causes of the DTC B3949 2018 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 2018 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 2018 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 2018 GMC Sierra code?

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Need Help with the 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 2018 GMC Sierra Code

1. What are the common symptoms of OBDII code B3949 on a 2018 GMC Sierra related to the Right Front Turn Signal Circuit?

The common symptoms include the right front turn signal not functioning properly or flickering intermittently.

2. What are the possible causes of OBDII code B3949 on a 2018 GMC Sierra?

Possible causes include a faulty right front turn signal bulb, a damaged wiring harness, a defective turn signal switch, or a problem with the body control module.

3. How can I troubleshoot OBDII code B3949 on my 2018 GMC Sierra?

You can start by checking the condition of the right front turn signal bulb, inspecting the wiring for any visible damage, and testing the turn signal switch for proper functionality.

4. Can a DIY enthusiast repair OBDII code B3949 on a 2018 GMC Sierra?

Yes, depending on the cause of the code, a DIY enthusiast with the necessary tools and skills can replace a faulty bulb, repair a damaged wire, or replace a defective turn signal switch.

5. Is it important to address OBDII code B3949 promptly on a 2018 GMC Sierra?

Yes, it is important to address the code promptly to ensure proper operation of the right front turn signal for safety reasons and to prevent potential issues with the vehicle's electrical system.

6. What are the potential risks of ignoring OBDII code B3949 on a 2018 GMC Sierra?

Ignoring the code could lead to safety hazards on the road, such as reduced visibility when making right turns, which may increase the risk of accidents.

7. How much does it typically cost to repair OBDII code B3949 on a 2018 GMC Sierra at a professional auto repair shop?

The cost of repairing the code can vary depending on the cause and the labor rates of the repair shop, but it may range from $50 to $200 or more.

8. Can OBDII code B3949 on a 2018 GMC Sierra be cleared with a diagnostic scanner after the issue is resolved?

Yes, once the underlying issue causing the code is fixed, it can be cleared using a diagnostic scanner to reset the vehicle's computer system.

9. Are there any recalls or technical service bulletins related to OBDII code B3949 on a 2018 GMC Sierra?

It is recommended to check with a GMC dealership or visit the National Highway Traffic Safety Administration (NHTSA) website to see if there are any relevant recalls or bulletins related to this code.

10. How often does OBDII code B3949 related to the Right Front Turn Signal Circuit occur in a 2018 GMC Sierra?

The occurrence of this specific code can vary depending on factors such as vehicle usage, maintenance, and driving conditions, but it is not considered a common issue.