AutoCodes – Lexus – P0B42 Lexus

P0B42 Lexus Code - Hybrid Battery Voltage Sense 'B' Circuit Low

Quick Answer

The HV battery uses nickel metal-hydride batteries and does not require external charging. Common causes include Faulty Battery smart unit, Faulty HV battery assembly. 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: P0B42 Lexus indicates Hybrid Battery Voltage Sense 'B' Circuit Low.
Common causes: Common causes include Faulty Battery smart unit, Faulty HV battery assembly.
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 2,715

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 Mar 07, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P0B42 Lexus Description

The HV battery uses nickel metal-hydride batteries and does not require external charging. The power management control ECU controls the SOC (state of charge) of the HV battery at a constant level during driving. The HV battery is composed of 28 modules, and each module consists of eight 1.2 V cells in series. The battery smart unit monitors battery block voltage at 14 locations. Each battery block is composed of 2 modules in a set. The battery smart unit, which monitors the voltage of the battery blocks, determines that malfunction has occurred if a voltage difference between the battery blocks exceeds the standard. When the malfunction detection condition is satisfied, the power management control ECU (HV CPU) will illuminates the Malfunction Indicator Lamp (MIL) and set a Diagnostic Trouble Code (DTC).

OBDII Code P0B42 Lexus - Hybrid Battery Voltage Sense 'B' Circuit Low - AutoCodes.com — P0B42 Lexus Code - Hybrid Battery Voltage Sense 'B' Circuit Low

What does this mean?

What are the Possible Causes of the DTC P0B42 Lexus?

Faulty Battery smart unit
Faulty HV battery assembly

How to Fix the DTC P0B42 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 P0B42 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.

Frequently Asked Questions about P0B42 Lexus Code

What does the OBDII code P0B42 mean on a Lexus?

1. The P0B42 code indicates a low voltage issue in the Hybrid Battery Voltage Sense 'B' Circuit, which monitors the voltage of specific battery modules in the hybrid system. 2.

What are the common symptoms of a P0B42 code in a Lexus?

Symptoms may include the hybrid system warning light turning on, reduced fuel efficiency, limited power output, or the vehicle entering limp mode. 3.

What causes the P0B42 code to appear in a Lexus?

Common causes include a faulty hybrid battery module, a damaged or corroded voltage sense wiring harness, a defective battery voltage sensor, or issues with the hybrid battery ECU. 4.

Can I drive my Lexus with a P0B42 code?

While you may still be able to drive the vehicle, continuing to do so could result in further damage to the hybrid battery system. It’s best to have the issue diagnosed and repaired promptly. 5.

How is the P0B42 code diagnosed in a Lexus?

A technician will typically use a scan tool to confirm the code, inspect the hybrid battery voltage sense circuit for damage, and test the battery voltage sensor and related wiring. 6.

How do you fix the P0B42 code in a Lexus?

Repairs may include replacing a faulty hybrid battery module, repairing or replacing damaged wiring or connectors in the voltage sense circuit, or replacing the hybrid battery ECU if needed. 7.

Is the P0B42 code specific to Lexus hybrid vehicles?

Yes, this code is specific to hybrid vehicles, including Lexus models, as it relates to the hybrid battery voltage sense circuit. 8.

How much does it cost to repair a P0B42 code on a Lexus?

Repair costs can vary widely depending on the root cause, ranging from around $150 for minor wiring repairs to over $2,000 if the hybrid battery or ECU needs replacement. 9.

Can a weak hybrid battery cause the P0B42 code?

Yes, a failing or degraded hybrid battery can cause voltage irregularities that trigger the P0B42 code. 10.

Will resetting the code fix the P0B42 issue on a Lexus?

Resetting the code may clear the warning temporarily, but it won’t fix the underlying issue. The problem must be properly diagnosed and repaired to prevent the code from returning.