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P0031 Lexus Code - Oxygen Air-Fuel Ratio Sensor Heater Control Circuit Low Bank 1 Sensor 1

- Code Popularity: 51,883 Views
- Repair Importance Level: 2/3
- Repair Difficulty Level: 2/3
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What are the Possible Causes of the DTC P0031 Lexus?

NOTE: The causes shown may not be a complete list of all potential problems, and it is possible that there may be other causes.
  • Faulty Air-Fuel Ratio (A/F) Sensor Bank 1 Sensor 1
  • Air-Fuel Ratio Sensor Bank 1 Sensor 1 harness is open shorted to ground
  • Air-Fuel Ratio Sensor Bank 1 Sensor 1 circuit poor electrical connection
  • Faulty Engine Control Module (ECM)
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How to Fix the DTC P0031 Lexus?

Review the 'Possible Causes' mentioned above and visually examine the corresponding wiring harness and connectors. Ensure to check for any damaged components and inspect the connector pins for signs of being broken, bent, pushed out, or corroded.

Code Tech Notes

There is a Factory Service Bulletin for the 2004-2005 Lexus ES 330:
2004-2005 Lexus ES 330 Factory Service Bulletin OBDII Code P0031

Search for P0031 Lexus Questions and Answers: Search here →

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0031 Lexus code, it typically requires 1.0 hour of labor. The specific diagnosis time and labor rates at auto repair shops can differ based on factors such as the location, make and model of the vehicle, and even the engine type. It is common for most auto repair shops to charge between $75 and $150 per hour.

What are Code Possible Symptoms?

  • Engine Light ON (or Service Engine Soon Warning Light)

Code P0031 Lexus Description

The Engine Control Module (ECM) uses information from the air-fuel ratio sensor to regulate the air-fuel ratio and keep it close to the stoichiometric level. This maximizes the ability of the three-way catalytic converter to purify the exhaust gases.
The air-fuel ratio sensor detects oxygen levels in the exhaust gas and transmits the information to the ECM. The inner surface of the sensor element is exposed to the outside air. The outer surface of the sensor element is exposed to exhaust gas. The sensor element is made of platinum-coated zirconia and includes an integrated heating element.
The zirconia element generates a small voltage when there is a large difference in the oxygen concentrations between the exhaust gas and outside air. The platinum coating amplifies this voltage generation.
The air-fuel ratio sensor is more efficient when heated. When the exhaust gas temperature is low, the sensor cannot generate useful voltage signals without supplementary heating. The ECM regulates supplementary heating using a duty-cycle approach to adjust the average current in the sensor heater element. If the heater current is outside the normal range, the signal transmitted by the air-fuel ratio sensor becomes inaccurate. As a result, the ECM is unable to regulate the air-fuel ratio properly.
When the current in the air-fuel ratio sensor heater is outside the normal operating range, the ECM interprets this as a malfunction in the sensor heater and stores a Diagnostic Trouble Code (DTC).

OBDII Code P0031 Lexus - Oxygen Air-Fuel Ratio Sensor Heater Control Circuit Low Bank 1 Sensor 1 - AutoCodes.com
P0031 Lexus Code - Oxygen Air-Fuel Ratio Sensor Heater Control Circuit Low Bank 1 Sensor 1

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