AutoCodes – Generic – B1508

B1508 Code - Flash To Pass Switch Circuit Open

Quick Answer

The Smart Junction Box (SJB) sends reference signals to the headlamp switch through circuits. 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: B1508 indicates Flash To Pass Switch Circuit Open.
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 7,917

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 Apr 29, 2019

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code B1508 Description

The Smart Junction Box (SJB) sends reference signals to the headlamp switch through circuits. When the headlamp switch is placed in the HEADLAMPS ON position, the voltage signal is routed to ground through the circuit. If the SJB detects a fault with the headlamp switch inputs, the SJB turns the exterior lamps on by default. When the SJB detects the headlamp switch in the HEADLAMPS ON position and the multifunction switch in the LOW BEAM position, the SJB sends voltage through circuits to the low beam headlamps. When the SJB detects the headlamp switch in the HEADLAMPS ON position and the multifunction switch in the HIGH BEAM position, the SJB sends voltage through circuits to the high beam headlamps. The SJB sends a reference signal to the multifunction switch through circuits CLF27 (GN/BN) and CLF17 (WH/OG). When the multifunction switch is placed in the FLASH-TO-PASS or HIGH BEAM position, the voltage signal is routed to ground. When the SJB detects a request for the flash-to-pass, the SJB sends voltage to the high beam headlamps. The OBDII codes when the SJB detects a short to ground from the flash-to-pass input circuit.

OBDII Code B1508 - Flash To Pass Switch Circuit Open - AutoCodes.com — B1508 Code - Flash To Pass Switch Circuit Open

What does this mean?

What are the Possible Causes of the DTC B1508?

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 B1508?

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 B1508 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 B1508 code?

Need more information on how to fix the B1508 code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the B1508 code diagnosed by a professional: Find a repair shop in your area

Information for Specific Makes

B1508 Buick — Low Voltage On Control Circuit
B1508 Cadillac — Low Voltage On Control Circuit
B1508 Chevrolet — Low Voltage On Control Circuit
B1508 Ford — Flash To Pass Switch Circuit Open
B1508 GMC — Low Voltage On Control Circuit
B1508 Lexus — Short In Turn Signal / Hazard Flasher Circuit
B1508 Lincoln — Flash To Pass Switch Circuit Open
B1508 Mercury — Flash To Pass Switch Circuit Open
B1508 Toyota — Short In Turn Signal / Hazard Flasher 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 B1508 Code

What does the OBDII code B1508 mean?

The OBDII code B1508 indicates that there is an open circuit in the Flash To Pass switch, which typically controls the vehicle's high beam headlights.

What symptoms might I experience with a B1508 code?

Common symptoms include malfunctioning high beams, inability to flash headlights, or dashboard warning lights related to the lighting system.

What could cause the B1508 code?

Causes of the B1508 code may include a faulty Flash To Pass switch, damaged wiring or connectors in the circuit, or issues with the body control module (BCM).

How can I diagnose the B1508 code?

To diagnose the B1508 code, start by visually inspecting the Flash To Pass switch and related wiring for damage. Use a multimeter to check for continuity in the circuit and ensure the switch is functioning properly.

What is the typical repair for a B1508 code?

Repairs may involve replacing the Flash To Pass switch, repairing or replacing damaged wiring, or, in some cases, reprogramming or replacing the body control module.

Is it safe to drive with a B1508 code?

While you may still have functioning headlights, it is not advisable to drive with a B1508 code, as this could affect your visibility and safety, especially at night or in low-light conditions.

Can I clear the B1508 code after repairs?

Yes, after performing the necessary repairs, you can use an OBDII scanner to clear the B1508 code and reset the system. Monitor for any reoccurrence of the code.

Will a bad battery affect the B1508 code?

Yes, a weak or failing battery can cause electrical issues that may trigger the B1508 code, so it's a good idea to check the battery's condition as part of the diagnostic process.

How much does it typically cost to fix the B1508 code?

Repair costs can vary widely depending on the cause, ranging from a simple switch replacement costing around $50 to $200, to more extensive wiring repairs or module replacements that could exceed $500.