Possible causes

– Faulty Air Fuel Ratio Sensor 1 Bank 1
– Air Fuel Ratio Sensor 1 harness is open or shorted
– Air Fuel Ratio Sensor 1 circuit poor electrical connection

Tech notes

There is a factory service bulletin for the following Infiniti models:

2004-2005 Infiniti FX35
2004-2005 Infiniti FX45
2004-2005 Infiniti G35 Sedan
2004-2005 Infiniti G35 Sedan
Infiniti Factory Service Bulletin OBDII Code P1031

The bulletin suggest reprogramming the Engine Control Module (ECM) first before replacing any parts.

When is the code detected?

The current amperage in the heated air fuel ratio (A/F) sensor 1 heater circuit is out of the normal range. An excessively low voltage signal is sent to Engine Control Module (ECM) through the heated air fuel ratio (A/F) sensor 1 heater.

Symptoms

– Engine Light ON (or Service Engine Soon Warning Light)

P1031 INFINITI Description

The Engine Control Module (ECM) performs ON/OFF duty control of the Air Fuel Ratio (A/F) sensor 1 heater corresponding to the engine operating condition to keep the temperature of A/F sensor 1 element at the specified range.

INFINITI Technical Service Bulletins for P1031 code