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On-board diagnostic (OBD) codes help mechanics and vehicle owners identify possible issues in a vehicle. But before you can troubleshoot and resolve these problems, it’s important to know what these codes mean.

Code P0031 is one of many trouble codes that may be logged and retrieved from the OBD system. Here is some basic information that may help you understand what getting this code may mean for your vehicle.

obd scan
Code P0031 is one of many trouble codes that may be logged and retrieved from the OBD system.

What Does the P0031 Code Mean?

Diagnostic trouble code (DTC) P0031 stands for “HO2S Heater Control Circuit Low (Bank 1 Sensor 1).” This code is logged when the powertrain control module (PCM) detects that the actual and desired state of the oxygen sensor heater control circuit do not match.

The oxygen sensor referred to in this trouble code is the sensor located on Bank 1, in front of the catalytic converter. The purpose of this sensor is to measure the amount of oxygen present in the exhaust gas and compare this to the outside air. This data allows your car’s computer to make the necessary air-fuel ratio adjustments as both enter the engine.

For the oxygen sensor #1 to make an accurate reading, it must be at a certain temperature. A heater wire inside the sensor brings its temperature up whenever needed. When the PCM detects an excessively low voltage or if it perceives that the heater wire is failing, it sets the P0031 code.

Depending on the severity of the problem, related error codes may also be stored with this DTC. Code P0031 is very similar to error codes P0032, P0051, and P0052.

Users have reported P0031 for the following makes: Toyota (especially on a Toyota Camry), Nissan, Subaru, Infiniti, and Lexus.

Note: The definition of code P0031 may be different depending on the vehicle manufacturer. Consult the appropriate repair manual or repair database for the exact code definition.

What are the Possible Causes of the P0031 Code?

P0031 is a generic code, so it can have several triggers. Here are the most common:

  • O2 sensor heater circuit issues (damaged wires and poor connections)
  • Faulty O2 Sensor
  • Failure in the PCM or software in need of an update
1 oxygen sensor
For the oxygen sensor #1 to make an accurate reading, it must be at a certain temperature.

What are the Common Symptoms of the P0031 Code?

You may notice the following symptoms if you drive a vehicle that has set a P0031 trouble code:

  • Check engine light is illuminated
  • Poor engine performance
  • Excessive fuel consumption

How to Diagnose the P0031 Code

Error code P0031 is a generic code that may be set across several makes and models. However, this does not mean that there is a one-size-fits-all approach to diagnosing its underlying cause. The steps for troubleshooting this code will vary depending on your vehicle’s make and model.

Check out the video below to get an idea of what the diagnostic process for this code might involve:

How to Fix the P0031 Code

Although code P0031 shares similar triggers and symptoms with other engine codes, the appropriate diagnostic and repair procedure will depend on the specifications of your vehicle. If you’re unfamiliar with auto repair, you should leave the job to a mechanic.

If you’re considering troubleshooting this code on your own, it’s a good idea to refresh your automotive knowledge before attempting any fixes. Always consult the vehicle repair manual or an online repair database to learn the appropriate diagnostic and repair procedures for this code.

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Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic.

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