AutoCodes – Lexus – P0043 Lexus

P0043 Lexus Code - HO2S Heater Control Circuit Low Bank 1 Sensor 3

Quick Answer

Oxygen Sensors (O2S) or Heated Oxygen Sensors (HO2S) need to reach a minimum operating temperature of 750 degrees F to produce an accurate voltage signal. Common causes include Faulty Heated Oxygen Sensor (H2OS) Bank 1 Sensor 3, Heated Oxygen Sensor (H2OS) Bank 1 Sensor 3 harness is open shorted, Heated Oxygen Sensor (H2OS) Bank 1 Sensor 3 circuit poor electrical connection. Severity is Moderate - service should be scheduled soon. The vehicle may still be drivable for short trips if it runs normally, but avoid hard driving and repair it soon.

What it means: P0043 Lexus indicates HO2S Heater Control Circuit Low Bank 1 Sensor 3.
Common causes: Common causes include Faulty Heated Oxygen Sensor (H2OS) Bank 1 Sensor 3, Heated Oxygen Sensor (H2OS) Bank 1 Sensor 3 harness is open shorted, Heated Oxygen Sensor (H2OS) Bank 1 Sensor 3 circuit poor electrical connection.
Severity: Moderate - service should be scheduled soon.
Can I drive?: The vehicle may still be drivable for short trips if it runs normally, but avoid hard driving and repair it soon.

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Code Popularity 4,973

How popular is this code, among other codes? Low

Repair Importance Level

Moderate (Service soon) (2 / 3)

Repair Difficulty Level

Intermediate (2 / 3)

What is this?

Table of contents Created and updated by William Orellana on Mar 23, 2024

Description
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
Comments
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Code P0043 Lexus Description

Oxygen Sensors (O2S) or Heated Oxygen Sensors (HO2S) need to reach a minimum operating temperature of 750 degrees F to produce an accurate voltage signal. The faster the heated oxygen sensor reaches that temperature the faster the sensor will start sending an accurate signal to the Engine Control Module (ECM).
In order to achieve the require temperature, a heater element is included inside the heated oxygen sensor. The ECM controls the heated oxygen sensor heater element based on signals from the engine coolant temperature and engine load. The ECM controls the heater element circuit by allowing current flow to ground.
The ECM monitors the voltage signal received through the heater element circuit and determines the state of the circuit by comparing the voltage detected with the factory specifications.

OBDII Code P0043 Lexus - HO2S Heater Control Circuit Low Bank 1 Sensor 3 - AutoCodes.com — P0043 Lexus Code - HO2S Heater Control Circuit Low Bank 1 Sensor 3

What does this mean?

What are the Possible Causes of the DTC P0043 Lexus?

Faulty Heated Oxygen Sensor (H2OS) Bank 1 Sensor 3
Heated Oxygen Sensor (H2OS) Bank 1 Sensor 3 harness is open shorted
Heated Oxygen Sensor (H2OS) Bank 1 Sensor 3 circuit poor electrical connection
Heated Oxygen Sensor (H2OS) Bank 1 Sensor 3 fuse
Faulty Engine Control Module (ECM)

How to Fix the DTC P0043 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 does this mean?

Code Tech Notes

The code means that there is a problem with the heater element circuit of the heated oxygen sensor. Water getting inside the heated oxygen sensor connector can caused the heated oxygen sensor fuse to blow, which is a very common problem for this type codes. Before replacing the sensor, check for the condition of the heated oxygen sensor fuse and connectors.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0043 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.