AutoCodes – GMC – B3950 2016 GMC Sierra

B3950 2016 GMC Sierra Code - Left Rear Turn Signal Circuit

Quick Answer

Ground is applied at all times to the turn signal/multifunction switch. Common causes include Faulty Left Rear Turn Signal Lamp, Left Rear Turn Signal Lamp harness is open or shorted, Left Rear 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: B3950 2016 GMC Sierra indicates Left Rear Turn Signal Circuit.
Common causes: Common causes include Faulty Left Rear Turn Signal Lamp, Left Rear Turn Signal Lamp harness is open or shorted, Left Rear 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 212

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Basic DIY (1 / 3)

What is this?

Table of contents Created and updated by William Orellana on Jun 17, 2023

Description
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
FAQs
Comments
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Code B3950 2016 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 a short to voltage, short to ground, or an open/high resistance in the left rear turn signal control circuit.

OBDII Code B3950 2016 GMC Sierra - Left Rear Turn Signal Circuit - AutoCodes.com — B3950 2016 GMC Sierra Code - Left Rear Turn Signal Circuit

What does this mean?

What are the Possible Causes of the DTC B3950 2016 GMC Sierra?

Faulty Left Rear Turn Signal Lamp
Left Rear Turn Signal Lamp harness is open or shorted
Left Rear Turn Signal Lamp circuit poor electrical connection

How to Fix the DTC B3950 2016 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 does this mean?

Code Tech Notes

B3950:01 Left Rear Turn Signal Circuit Short to Battery
B3950:02 Left Rear Turn Signal Circuit Short to Ground
B3950:04 Left Rear Turn Signal Circuit Open

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the B3950 2016 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.

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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 B3950 2016 GMC Sierra Code

1. What does the OBDII code B3950 mean on a 2016 GMC Sierra?

B3950 indicates an issue with the left rear turn signal circuit, such as an open or short in the wiring, a faulty bulb, or a problem with the related control module.

2. What are the symptoms of code B3950 on a 2016 GMC Sierra?

Common symptoms include the left rear turn signal not working, hyper-flashing of the turn signal indicator, or a warning message on the dashboard.

3. What causes the B3950 code to appear on a 2016 GMC Sierra?

Causes may include a burned-out turn signal bulb, damaged wiring or connectors, corrosion at the bulb socket, or a malfunctioning Body Control Module (BCM).

4. How can I troubleshoot the B3950 code on a 2016 GMC Sierra?

Start by inspecting the left rear turn signal bulb and socket for damage or corrosion. Check the wiring and connectors for continuity or signs of wear. If all physical components are fine, scan the BCM for further faults.

5. Can I drive my 2016 GMC Sierra with the B3950 code active?

Itâ€™s not recommended, as a non-functioning turn signal can create safety hazards and may lead to traffic violations.

6. How do I fix the B3950 code on a 2016 GMC Sierra?

Replace the faulty turn signal bulb if necessary. Clean or repair corroded or damaged connectors and wiring. If the issue persists, the BCM may need to be reprogrammed or replaced.

7. How much does it cost to repair the B3950 code on a 2016 GMC Sierra?

Costs vary depending on the issue. A bulb replacement is inexpensive, typically under $20, while wiring or BCM repairs could cost $100-$500 or more.

8. Can a weak battery cause the B3950 code on a 2016 GMC Sierra?

A weak or failing battery is unlikely to directly cause the B3950 code but can lead to electrical malfunctions that might trigger other related issues.

9. Do I need special tools to diagnose the B3950 code on a 2016 GMC Sierra?

A multimeter is helpful for testing continuity in the wiring, and an OBDII scanner capable of reading BCM codes is recommended for accurate diagnosis.

10. Can a faulty fuse cause the B3950 code on a 2016 GMC Sierra?

Yes, a blown fuse in the turn signal circuit may result in the B3950 code. Check the fuse box and replace any blown fuses as part of your troubleshooting.