AutoCodes – Generic – B3948:04

B3948:04 Code - Left Front Turn Signal Circuit Open

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: B3948:04 indicates Left Front Turn Signal Circuit Open.
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 738

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 B3948:04 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 B3948:04 - Left Front Turn Signal Circuit Open - AutoCodes.com — B3948:04 Code - Left Front Turn Signal Circuit Open

What does this mean?

What are the Possible Causes of the DTC B3948:04?

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 B3948:04?

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 B3948:04 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 B3948:04 Code

1. What are the common symptoms of OBDII code B3948:04 (Left Front Turn Signal Circuit Open)?

- The common symptoms include the left front turn signal not working, fast blinking of the turn signal, or a warning light on the dashboard.

2. What are the possible causes of OBDII code B3948:04?

- The code may be triggered by a damaged or disconnected wire in the left front turn signal circuit, a faulty turn signal bulb, or a problem with the turn signal switch.

3. How can I diagnose the issue related to OBDII code B3948:04?

- You can start by visually inspecting the left front turn signal bulb, checking the wiring for any damage, and testing the turn signal switch for proper functionality.

4. What are some repair tips for fixing OBDII code B3948:04?

- Repair tips include repairing or replacing any damaged wires in the circuit, replacing the left front turn signal bulb if necessary, and ensuring proper connection of components.

5. Can I reset the OBDII code B3948:04 without fixing the issue?

- While you can clear the code with an OBDII scanner, it is recommended to address the underlying issue causing the code to prevent further problems with the turn signal system.

6. Is it safe to continue driving with OBDII code B3948:04 active?

- It is not recommended to drive with the code active as it indicates a malfunction in the turn signal circuit, which can affect your vehicle's visibility to other drivers and compromise safety.

7. How much does it typically cost to repair OBDII code B3948:04?

- The cost of repair can vary depending on the exact cause of the issue, but it may involve relatively simple repairs like replacing a bulb or can be more extensive if there is wiring damage.

8. Can extreme weather conditions trigger OBDII code B3948:04?

- Yes, extreme weather conditions like heavy rain or snow can potentially cause water damage to the turn signal circuit, leading to the circuit being open and triggering the code.

9. Are there any preventive measures to avoid OBDII code B3948:04 in the future?

- Regularly inspecting and maintaining your vehicle's turn signal system, keeping an eye on the functionality of the turn signals, and addressing any issues promptly can help prevent this code from occurring.

10. Does OBDII code B3948:04 affect other vehicle systems?

- While the code specifically relates to the left front turn signal circuit, it can indirectly affect overall vehicle safety by impacting turn signal functionality, especially during driving maneuvers.