AutoCodes – Generic – B1578

B1578 Code - Lamp Park Input Circuit Short To Ground

Quick Answer

The Smart Junction Box (SJB) monitors the parking lamp request input from the headlamp switch. Common causes include Faulty Headlamp Switch, Headlamp Switch harness is open or shorted, Headlamp Switch 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: B1578 indicates Lamp Park Input Circuit Short To Ground.
Common causes: Common causes include Faulty Headlamp Switch, Headlamp Switch harness is open or shorted, Headlamp Switch 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 10,288

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 Feb 26, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code B1578 Description

The Smart Junction Box (SJB) monitors the parking lamp request input from the headlamp switch. The SJB provides a ground for the parking lamp relay coil (integrated into the SJB ) when a request for the parking lamps is received. When the parking lamp relay is energized, voltage is routed to the rear and front parking lamps. The Diagnostic Trouble Code (DTC) sets when the SJB detects a short to ground from the parking lamps on input circuit.

OBDII Code B1578 - Lamp Park Input Circuit Short To Ground - AutoCodes.com — B1578 Code - Lamp Park Input Circuit Short To Ground

What does this mean?

What are the Possible Causes of the DTC B1578?

Faulty Headlamp Switch
Headlamp Switch harness is open or shorted
Headlamp Switch circuit poor electrical connection
Faulty Smart Junction Box (SJB)

How to Fix the DTC B1578?

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 B1578 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 B1578 code?

Need more information on how to fix the B1578 code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the B1578 code diagnosed by a professional: Find a repair shop in your area

Information for Specific Makes

B1578 Chrysler — Audio Antenna Circuit Resistance Below Threshold
B1578 Dodge — Audio Antenna Circuit Resistance Below Threshold
B1578 Ford — Lamp Park Input Circuit Short To Ground
B1578 Jeep — Audio Antenna Circuit Resistance Below Threshold
B1578 Lincoln — Lamp Park Input Circuit Short To Ground
B1578 Mercury — Lamp Park Input Circuit Short To Ground
B1578 RAM — Audio Antenna Circuit Resistance Below Threshold

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 B1578 Code

1. What are the common symptoms of OBDII code B1578 (Lamp Park Input Circuit Short To Ground)?

- Common symptoms include the illumination of the malfunction indicator lamp (MIL) or check engine light, and issues with the park lamps or exterior lighting.

2. What are the possible causes of OBDII code B1578?

- The code B1578 can be caused by a short to ground in the lamp park input circuit, faulty wiring or connectors, or a malfunctioning lamp park input sensor.

3. How can I diagnose the OBDII code B1578?

- Diagnosing code B1578 involves using a scan tool to retrieve the trouble codes, inspecting the wiring and connectors for damage, and testing the lamp park input sensor for proper operation.

4. Can a DIY enthusiast repair OBDII code B1578?

- Depending on the underlying cause, a DIY enthusiast may be able to repair code B1578 by replacing damaged wiring or connectors, or by replacing the faulty lamp park input sensor.

5. Are there any safety precautions to consider when repairing OBDII code B1578?

- When working on the lamp park input circuit, ensure that the vehicle's electrical system is disconnected to prevent any risk of electric shock or short circuits.

6. How can I prevent OBDII code B1578 from recurring?

- To prevent code B1578 from recurring, perform regular inspections of the vehicle's exterior lighting system, and address any issues promptly to avoid potential shorts or malfunctions.

7. Can OBDII code B1578 cause any other problems in the vehicle?

- While code B1578 primarily indicates a fault in the lamp park input circuit, unresolved issues with the vehicle's lighting system can affect visibility and safety on the road.

8. Is it safe to drive with OBDII code B1578 present?

- It is generally safe to drive with code B1578, but it is recommended to address the issue promptly to ensure the proper operation of the vehicle's lighting system.

9. How long does it typically take to repair OBDII code B1578?

- The repair time for code B1578 can vary depending on the exact cause of the issue, but it may take anywhere from 30 minutes to a few hours to diagnose and fix the problem.

10. Can a mechanic reset the OBDII code B1578 after repairs are completed?

- Yes, a mechanic can reset the OBDII code B1578 using a scan tool after the necessary repairs have been made to clear the code from the vehicle's memory.