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

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.

• 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.

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

• 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.