AutoCodes – Buick – B3950 Buick

B3950 Buick 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 Buick 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 1,219

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 Buick 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 Buick - Left Rear Turn Signal Circuit - AutoCodes.com — B3950 Buick Code - Left Rear Turn Signal Circuit

What does this mean?

What are the Possible Causes of the DTC B3950 Buick?

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 Buick?

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 Buick 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 Buick Code

1. What are the common symptoms of OBDII code B3950 Buick 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, or a dashboard warning light indicating a turn signal fault.

2. What are the possible causes of OBDII code B3950 Buick for the Left Rear Turn Signal Circuit?

Potential causes can include a faulty turn signal bulb, a damaged wiring harness, a malfunctioning turn signal switch, or a problem with the body control module.

3. How can I diagnose the issue causing OBDII code B3950 for the Left Rear Turn Signal Circuit?

You can start by visually inspecting the left rear turn signal bulb, checking the wiring for any visible damage, testing the turn signal switch, and using a diagnostic scanner to read the specific fault codes.

4. What are some DIY repair tips for fixing OBDII code B3950 Buick related to the Left Rear Turn Signal Circuit?

You can try replacing the left rear turn signal bulb, repairing any damaged wiring, cleaning or replacing the turn signal switch, or resetting the body control module to see if the issue resolves.

5. Is it safe to continue driving with OBDII code B3950 Buick triggered for the Left Rear Turn Signal Circuit?

It is not recommended to drive with a malfunctioning turn signal, as it can pose a safety hazard to you and other drivers on the road. Promptly address the issue to ensure proper signaling.

6. Can a faulty fuse cause OBDII code B3950 Buick to appear for the Left Rear Turn Signal Circuit?

While a blown fuse can affect the turn signal operation, it may not directly trigger this specific diagnostic trouble code. However, checking the fuse for the turn signal circuit is still a good troubleshooting step.

7. How much does it typically cost to repair OBDII code B3950 Buick associated with the Left Rear Turn Signal Circuit?

The cost of repair can vary depending on the underlying cause of the issue. Simple fixes like bulb replacement may cost around $10-$20, while more complex repairs involving wiring or module replacement can range from $100 to $300 or more.

8. Can weather conditions impact the occurrence of OBDII code B3950 Buick for the Left Rear Turn Signal Circuit?

Extreme weather conditions, such as heavy rain or snow, can potentially exacerbate existing issues with the turn signal circuit. Moisture intrusion or exposure to the elements may lead to electrical malfunctions.

9. Are there any recalls or technical service bulletins related to OBDII code B3950 Buick concerning the Left Rear Turn Signal Circuit?

It's advisable to check with your local Buick dealership or visit the National Highway Traffic Safety Administration (NHTSA) website to see if there are any relevant recalls or technical service bulletins addressing this specific OBDII code.

10. Will resetting the OBDII system clear the B3950 code for the Left Rear Turn Signal Circuit?

Resetting the OBDII system may temporarily clear the code, but if the underlying issue causing the fault is not addressed, the code is likely to reappear. It's essential to diagnose and fix the root cause of the problem for a lasting solution.