What the OBD-II code p0031 means

Fault code P0031 – a step-by-step guide to diagnosing and fixing it

The meaning of error code P0031 – Oxygen (A/F) Sensor Heater Control Circuit Low (Bank 1 Sensor 1)
P0031
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P0031: causes, symptoms and repairs

The meaning of fault code P0031

DTC P0031 is triggered when the control unit detects a low voltage in the oxygen sensor heater circuit located on the first cylinder block of the engine. This oxygen sensor is used to monitor the oxygen concentration of oxygen in the exhaust gases and the car's engine control unit adjusts the air-fuel ratio accordingly. If the code is registered. It indicates that the heater isn’t working properly, meaning that the lambda device will take longer to warm up to the right operating temperature.

Possible causes

  • An open or short circuit, affecting the power supply. This can occur if the insulation sheath breaks or melts under certain voltage conditions or temperatures.
  • Frayed or damaged sensor/relay wires and connectors. These components can get damaged if they are installed incorrectly or come into contact with moving or very hot parts, such as exhaust components.
  • Corroded electrical contacts in the connectors, resulting from exposure to moisture or dirt.
  • A malfunctioning engine control module. If the ECM fails, it won’t be able to monitor or control the components effectively, triggering false codes.
  • A carbon-fouled or contaminated oxygen sensor (lambda probe). The sensor and heater can be affected by deposits which form when poor-quality fuel is used, the air-fuel mixture is too rich, or oil gets into the combustion chambers of the engine.
Symptoms of code P0031

  • A decline in fuel efficiency and engine performance
  • Activation of the check engine light
  • Engine hesitation
  • A rough idle
  • A decrease in power
Recommended repairs

  • First, you will need a proper diagnosis of the problem. To identify the possible causes of this DTC, connect an OBD2 scanner to the vehicle via the data link connector port. Scan the system and check the registered DTCs and freeze frame data.
  • Visually inspect the wires and connectors to the sensor and circuit relay for loose connections, corrosion, fraying, and other signs of damage. Replace any damaged parts. Make sure the components are installed properly.
  • Remove oily or carbon deposits from the lambda probe and traces of oxidation from the electrical connectors to restore the power supply and electrical connections. These parts should be cleaned using specialised products that are designed to improve conductivity, such as an O2 sensor cleaner.
  • Remember to check the electrical resistance of the heater to detect circuit problems. You can measure this with a multimeter and then compare the measurements to the standard values for this device. If the component is faulty, install a new one.
Frequently Asked Questions (FAQ)

What does the code “P0031” mean?


It means that a fault has been detected in the heater circuit of the oxygen sensor on bank 1, which is normally located in front of the catalytic converter.

How do I get rid of this DTC?


It can be reset and erased from the computer’s memory archive using an OBD2 scan tool. However, if it reappears, you will need to investigate the fault further and fix the O2 device.

Can I still drive my car if this occurs?


The fault will affect the driveability of the vehicle as well as its fuel consumption. Although the car may still be able to run without any major problems, a failing sensor can have a serious impact on key components such as the catalytic converter. It is therefore advisable to refrain from driving until the issue is addressed.

Cars the fault code P0031 is most commonly found on

Fault code P0031 - Oxygen (A/F) Sensor Heater Control Circuit Low (Bank 1 Sensor 1) can occur with any car but is most often found on the following cars:

  • Subaru: WRX, Forester
  • Nissan: Micra, 350Z, Almera
  • Toyota: Avensis, Prius, Camry
  • Mazda: 3, 2
  • Suzuki: Grand Vitara, Swift, SX4
  • Peugeot: 207

If you get the code P0031 on your car, make sure that the diagnostics are carried out correctly and the error is still relevant. Check for symptoms associated with the problem and explore options for resolving it.

What to do if the fault code p 0031 appears

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