AutoCodes – Generic – B178E

B178E Code - Headlamp Switch Input Circuit Short to Ground

Quick Answer

The Body Control Module (BCM) receives an input voltage 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: B178E indicates Headlamp Switch 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.

Save to My Repairs My Repairs

AI answers can be wrong. Verify repairs with testing. Open full chat

Code Popularity 76

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 Nov 05, 2025

Description
Possible Causes
How To Fix
Cost to Diagnose
Comments
Add Comment

💬 Need more help? Ask Coddy for instant answers — it's free!

Code B178E Description

The Body Control Module (BCM) receives an input voltage from the headlamp switch. The BCM monitors the headlamp switch voltage and controls the exterior lighting functions based on the switch input. For additional information on Headlamp Switch operation. The Diagnostic Trouble Code (DTC) will be set when the BCM detects a low condition on the Headlamp Switch MUX circuit.

OBDII Code B178E - Headlamp Switch Input Circuit Short to Ground - AutoCodes.com — B178E Code - Headlamp Switch Input Circuit Short to Ground

What does this mean?

What are the Possible Causes of the DTC B178E?

Faulty Headlamp Switch
Headlamp Switch harness is open or shorted
Headlamp Switch circuit poor electrical connection
Faulty Diagnostic Trouble Code (DTC)

How to Fix the DTC B178E?

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 B178E 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 B178E code?

Need more information on how to fix the B178E code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the B178E code diagnosed by a professional: Find a repair shop in your area

Information for Specific Makes

B178E Chrysler — Headlamp Switch Input Circuit Short to Ground
B178E Dodge — Headlamp Switch Input Circuit Short to Ground
B178E Jeep — Headlamp Switch Input Circuit Short to Ground
B178E RAM — Headlamp Switch Input Circuit Short to Ground

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.