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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.

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.

oxygen sensor installed in a modern car
For the oxygen sensor #1 to make an accurate reading, it must be at a certain temperature.

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.

See also  How to Unblock a Catalytic Converter

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.

For more information that can help you find a DIY fix for P0031, read our technical discussion about why oxygen sensors need heat. Make sure that you also know where bank 1 and bank 2 are before doing any DIY diagnosis or troubleshooting.

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
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Man hold in hand faulty old oxygen sensor with engine in the background
A faulty oxygen sensor can cause the P0031 Code.

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:

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.

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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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About The Authors
Richard McCuistian, ASE Certified Master Automobile Technician
Richard McCuistian, ASE Certified Master Automobile Technician

Technical Reviewer at

Richard McCuistian has worked for nearly 50 years in the automotive field as a professional technician, an instructor, and a freelance automotive writer for Motor Age, ACtion magazine, Power Stroke Registry, and others. Richard is ASE certified for more than 30 years in 10 categories, including L1 Advanced Engine Performance and Light Vehicle Diesel.

CarParts Research Team Research Team

Automotive and Tech Writers

The Research Team is composed of experienced automotive and tech writers working with (ASE)-certified automobile technicians and automotive journalists to bring up-to-date, helpful information to car owners in the US. Guided by's thorough editorial process, our team strives to produce guides and resources DIYers and casual car owners can trust.

Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.

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