Error P0031 on Infiniti cars

The P0031 code on Infiniti vehicles indicates a problem with a low voltage in the oxygen (O2) sensor heater control circuit (HO2S Heater Control Circuit Low). This means that the engine control module (ECM) has detected low voltage in the oxygen sensor heater circuit.

This is a serious failure, since improper operation of the oxygen sensor can lead to problems with the fuel system, which, as a result, reduces engine performance and increases harmful emissions.

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• Infiniti DTC — Diagnostic Trouble Code (OBD II)

• The Check Engine Light will come on.
• Fuel is not being used efficiently
• Harmful emissions will increase.
• The engine is idling or misfiring.

Trouble code P0031 can be caused by several issues, including:

• faulty O2 sensor.
• shorted, open, or corroded wiring or connectors in the O2 sensor heater circuit.
• blown fuse in the O2 sensor heater circuit.
• faulty ECM (although this is a less common cause).

• When low voltage is detected in the oxygen sensor heater circuit, the engine control module (ECM) may switch to a fallback mode, using a richer fuel map. This leads to increased fuel consumption.
• Incorrect information from the oxygen sensor will cause the engine to run rough at idle.
• Increased emissions.
• The P0031 code will cause the "Check Engine" indicator to appear on the instrument cluster.

Diagnosis involves using an OBD-II scanner to read stored codes. A visual inspection of the O2 sensor and associated wiring should then be performed to look for any signs of damage. If necessary, a digital multimeter is used to check for voltage in the heater circuit.

Repairing the problem may involve replacing a faulty sensor, repairing or replacing damaged wiring. A blown fuse may need to be replaced, and in rare cases, if the ECM is the root cause, it may need to be replaced or reprogrammed.