AutoCodes – Chevrolet – B3948 Chevrolet

B3948 Chevrolet Code - Left Front Turn Signal Circuit

Quick Answer

Ground is applied at all times to the turn signal/multifunction switch. Common causes include Faulty Left Front Turn Signal Lamp, Left Front Turn Signal Lamp harness is open or shorted, Left 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: B3948 Chevrolet indicates Left Front Turn Signal Circuit.
Common causes: Common causes include Faulty Left Front Turn Signal Lamp, Left Front Turn Signal Lamp harness is open or shorted, Left 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 7,837

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 B3948 Chevrolet 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 B3948 Chevrolet - Left Front Turn Signal Circuit - AutoCodes.com — B3948 Chevrolet Code - Left Front Turn Signal Circuit

What does this mean?

What are the Possible Causes of the DTC B3948 Chevrolet?

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

How to Fix the DTC B3948 Chevrolet?

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 B3948 Chevrolet 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 B3948 Chevrolet code?

Need more information on how to fix the B3948 Chevrolet code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the B3948 Chevrolet code diagnosed by a professional: Find a repair shop in your area

Information for Specific Chevrolet Models

B3948 2014 Chevrolet Silverado — Left Front Turn Signal Circuit
B3948 2015 Chevrolet Silverado — Left Front Turn Signal Circuit
B3948 2016 Chevrolet Silverado — Left Front Turn Signal Circuit
B3948 2017 Chevrolet Silverado — Left Front Turn Signal Circuit
B3948 2018 Chevrolet Silverado — Left Front Turn Signal Circuit

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 B3948 Chevrolet Code

1. What does the OBDII code B3948 mean on a Chevrolet?

B3948 indicates an issue with the left front turn signal circuit, often related to wiring, connections, or the turn signal bulb.

2. What are the common symptoms of the B3948 code?

Symptoms may include the left front turn signal not functioning, a fast or irregular flash rate, or a warning light on the dashboard.

3. What causes the B3948 code on a Chevrolet?

Common causes include a burned-out left front turn signal bulb, damaged wiring, corroded connectors, or a faulty turn signal switch.

4. How do I diagnose the B3948 code?

Start by inspecting the left front turn signal bulb for damage or burnout, check the wiring and connections for corrosion or breaks, and use a multimeter to test circuit continuity.

5. Can a bad bulb trigger the B3948 code?

Yes, a burned-out or faulty bulb is one of the most common reasons for this code to appear.

6. How do I fix the B3948 code on my Chevrolet?

Replace the left front turn signal bulb if itâ€™s burned out, repair or replace damaged wiring, and clean or secure any corroded or loose connectors.

7. Can the B3948 code cause other electrical issues in my vehicle?

While it is specific to the left front turn signal, unresolved circuit issues might affect other lighting or electrical systems if they share the same wiring harness.

8. How much does it cost to repair the B3948 code?

Replacing a turn signal bulb typically costs $10-$50, while wiring or connector repairs may range from $50 to $200 depending on the severity.

9. Can I drive my Chevrolet with the B3948 code?

Itâ€™s not recommended, as a malfunctioning turn signal reduces visibility and increases the risk of accidents, especially during lane changes or turns.

10. Do I need a professional to fix the B3948 code?

You can replace a bulb or inspect connectors yourself, but for complex wiring issues, itâ€™s best to consult a professional mechanic.