AutoCodes – GMC – B3950 2015 GMC Sierra

B3950 2015 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 2015 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 373
How popular is this code, among other codes? Low
Table of contents Created and updated by William Orellana on Jun 17, 2023
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Code B3950 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 a short to voltage, short to ground, or an open/high resistance in the left rear turn signal control circuit.
OBDII Code B3950 2015 GMC Sierra - Left Rear Turn Signal Circuit - AutoCodes.com
B3950 2015 GMC Sierra Code - Left Rear Turn Signal Circuit

What are the Possible Causes of the DTC B3950 2015 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 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.

Code Tech Notes

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the B3950 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.

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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 2015 GMC Sierra Code

1. What are the common symptoms of OBDII code B3950 in a 2015 GMC Sierra related to the left rear turn signal circuit?

The common symptoms include the left rear turn signal not working, fast blinking of the turn signal indicator on the dashboard, or a complete failure of the left rear turn signal.

2. What are some possible causes of OBDII code B3950 in a 2015 GMC Sierra?

Possible causes include a faulty left rear turn signal bulb, a damaged turn signal socket, a wiring issue in the left rear turn signal circuit, or a malfunctioning turn signal switch.

3. How can I diagnose the cause of OBDII code B3950 in my 2015 GMC Sierra's left rear turn signal circuit?

You can start by visually inspecting the left rear turn signal bulb and socket for any signs of damage. Check the wiring harness for any visible issues or loose connections. Using a multimeter, test the continuity of the wiring to identify any breaks or shorts.

4. Can I repair OBDII code B3950 in my 2015 GMC Sierra's left rear turn signal circuit myself?

Depending on the cause, you may be able to repair it yourself by replacing a faulty bulb, repairing a damaged socket, or fixing a wiring issue. However, if the problem is more complex, it may require professional diagnosis and repair.

5. Is it safe to drive my 2015 GMC Sierra with OBDII code B3950 affecting the left rear turn signal circuit?

Driving with a malfunctioning turn signal can be dangerous, as it may lead to accidents or traffic violations. It is recommended to address the issue promptly to ensure the proper functioning of your vehicle's turn signals.

6. Can a bad turn signal switch cause OBDII code B3950 in a 2015 GMC Sierra?

Yes, a malfunctioning turn signal switch can potentially cause OBDII code B3950 in the left rear turn signal circuit of a 2015 GMC Sierra. It is one of the possible causes that should be investigated during diagnosis.

7. How much does it typically cost to repair OBDII code B3950 in a 2015 GMC Sierra's left rear turn signal circuit?

The cost of repair can vary depending on the specific cause of the issue. Replacing a bulb or repairing a socket may be relatively inexpensive, while fixing a wiring problem or replacing a turn signal switch can be more costly.

8. Will resetting the OBDII code B3950 in my 2015 GMC Sierra make the left rear turn signal work again?

Resetting the code may temporarily turn off the warning light, but it will not fix the underlying issue causing the left rear turn signal malfunction. It is important to diagnose and repair the problem to ensure proper functionality.

9. Are there any preventive measures to avoid OBDII code B3950 in a 2015 GMC Sierra's left rear turn signal circuit?

Regularly inspecting and maintaining the turn signal bulbs, sockets, and wiring can help prevent issues like OBDII code B3950 from occurring. Addressing any minor problems promptly can help avoid more significant issues in the future.

10. Can extreme weather conditions affect the left rear turn signal circuit and trigger OBDII code B3950 in a 2015 GMC Sierra?

Extreme weather conditions such as heavy rain, snow, or intense heat can potentially damage the turn signal components, leading to malfunctions that trigger OBDII code B3950. It is essential to ensure the turn signal system is properly sealed and protected from the elements.

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