AutoCodes – Lexus – B243B Lexus

B243B Lexus Code - LED Wiring for High Beam Left Circuit

Quick Answer

This Diagnostic Trouble Code (DTC) is output when the headlight Electronic Control Unit (ECU) sub-assembly receives a high beam output malfunction signal from the headlight unit. Common causes include Faulty Headlight Unit Assembly Left (LH), Headlight Unit Assembly Left harness is open or shorted, Headlight Unit Assembly Left 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: B243B Lexus indicates LED Wiring for High Beam Left Circuit.
Common causes: Common causes include Faulty Headlight Unit Assembly Left (LH), Headlight Unit Assembly Left harness is open or shorted, Headlight Unit Assembly Left 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 45

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 Oct 03, 2025

Description
Possible Causes
How To Fix
Cost to Diagnose
Comments
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Code B243B Lexus Description

This Diagnostic Trouble Code (DTC) is output when the headlight Electronic Control Unit (ECU) sub-assembly receives a high beam output malfunction signal from the headlight unit. Note: If the No. 1 headlight ECU sub-assembly has been replaced; it is necessary to synchronize the vehicle information and initialize the No. 1 headlight ECU sub-assembly.

OBDII Code B243B Lexus - LED Wiring for High Beam Left Circuit - AutoCodes.com — B243B Lexus Code - LED Wiring for High Beam Left Circuit

What does this mean?

What are the Possible Causes of the DTC B243B Lexus?

Faulty Headlight Unit Assembly Left (LH)
Headlight Unit Assembly Left harness is open or shorted
Headlight Unit Assembly Left circuit poor electrical connection
Faulty Headlight Unit Left (LH)

How to Fix the DTC B243B Lexus?

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 B243B Lexus 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.