AutoCodes – Toyota – P0B42 Toyota

P0B42 Toyota 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 Toyota 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 15,456

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

What does this mean?

What are the Possible Causes of the DTC P0B42 Toyota?

Faulty Battery smart unit
Faulty HV battery assembly

How to Fix the DTC P0B42 Toyota?

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 Toyota 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 Toyota Code

What does the OBDII code P0B42 mean for a Toyota vehicle?

The P0B42 code indicates a problem with the Hybrid Battery Voltage Sense 'B' Circuit, specifically showing a low voltage condition detected by the hybrid battery control module.

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

Symptoms may include the hybrid system warning light activating, reduced fuel efficiency, limited electric vehicle (EV) mode, or reduced overall vehicle performance.

What causes the P0B42 code to appear in a Toyota hybrid?

Common causes include a faulty hybrid battery voltage sensor, damaged sensor wiring or connectors, corrosion in the circuit, or issues with the hybrid battery control module.

Can I drive my Toyota with the P0B42 code active?

While you may be able to drive the vehicle, it’s not recommended. The hybrid system may not function properly, potentially causing further damage to the hybrid components.

How is the P0B42 code diagnosed in a Toyota?

A technician will use a scan tool to confirm the code, inspect the hybrid battery voltage sensor and related wiring, and perform voltage tests to pinpoint the issue.

Can a loose connection cause the P0B42 code in a Toyota?

Yes, loose or corroded wiring connections in the voltage sense circuit can trigger this code by disrupting the sensor’s communication with the control module.

Is replacing the hybrid battery necessary to fix the P0B42 code?

Not always. The issue might be with the voltage sensor, wiring, or connectors rather than the battery itself. Proper diagnosis is crucial before replacing any components.

How much does it typically cost to repair the P0B42 code in a Toyota?

Repair costs vary widely depending on the root cause but can range from $150 to $1,000, with sensor or wiring repairs being less expensive than battery replacement.

Can a weak hybrid battery cause the P0B42 code?

Yes, a weak or failing hybrid battery can sometimes lead to this code, as the voltage levels may drop below the specified threshold.

What maintenance can help prevent the P0B42 code in a Toyota?

Regular inspections of the hybrid system wiring, keeping electrical connections clean and secure, and promptly addressing any warning lights can help prevent this issue.