INFINITI FX35 (2004-2012) Air/Fuel Ratio Sensor: A Comprehensive Guide
Everything an FX35 owner needs to know about diagnosing and replacing a faulty air/fuel ratio sensor.
- Stick with Denso or NGK/NTK brands for an aftermarket replacement; they are the OEM suppliers and offer the same quality as the dealer part for less money.
- A Check Engine Light for code P0101 on 2010-2012 models may be a dirty throttle body, not a bad sensor.
- The sensors are often seized in the exhaust; removal can be difficult and may require heat, penetrating oil, and a special O2 sensor socket.
- Your FX35 has two upstream Air/Fuel Ratio sensors (Bank 1/Passenger, Bank 2/Driver) and two downstream O2 sensors; ensure you order the correct part for the specific location.
Is Your INFINITI FX35 Air/Fuel Sensor Failing?
A failing air/fuel ratio sensor can cause noticeable problems with your vehicle's performance and efficiency. The most obvious sign is a Check Engine Light on your dashboard. However, other symptoms often appear even before the light comes on.
Key Symptoms of a Bad A/F Sensor:
- Poor Gas Mileage: One of the first things you might notice is more frequent trips to the gas station. A bad sensor can cause the engine to run too rich (too much fuel), wasting gas.
- Rough Idle: Your FX35 might idle unevenly, sputter, or even stall. The engine's computer struggles to maintain a stable mixture at low speeds without accurate sensor data.
- Sluggish Performance: If acceleration feels weak or delayed, the A/F sensor may be at fault. The engine isn't getting the right fuel mix for power when you need it.
- Failed Emissions Test: A faulty sensor leads to incomplete fuel combustion, which increases harmful pollutants in the exhaust and will cause your vehicle to fail a smog check.
Don't Mistake a MAF or Throttle Body Issue for a Bad Sensor
For 2010-2012 FX35 models, INFINITI issued a Technical Service Bulletin (ITB17-020) for a Check Engine Light with code P0101. This issue is often caused by a dirty throttle body, not a bad A/F sensor. Cleaning the throttle body may resolve the issue without needing to replace any sensors.
Choosing the Right Aftermarket A/F Sensor
When shopping for a replacement A/F sensor for your FX35, you'll find several options. For this specific vehicle, the choice between OEM and a top-tier aftermarket brand is less about quality and more about price.
Brand Quality: Denso and NGK/NTK
Denso and NGK (also sold under the brand name NTK) are the original equipment manufacturers (OEM) for many Japanese vehicles, including INFINITI. This means the Denso or NGK/NTK sensor you buy from an aftermarket retailer is often the exact same part that came on your FX35 from the factory, just without the INFINITI logo and associated dealer markup. Forum members and mechanics widely recommend sticking with these two brands for a reliable, direct-fit replacement that performs identically to the original.
Upstream vs. Downstream Sensors
Your FX35 has four sensors in total: two upstream Air/Fuel Ratio Sensors and two downstream Oxygen (O2) Sensors. The upstream A/F sensors do the primary work of fuel trim adjustment. The downstream O2 sensors mainly monitor the health of the catalytic converters. It is crucial to order the correct sensor for the position you are replacing (e.g., Upstream Bank 1).
Cost of Replacing an Air/Fuel Ratio Sensor on a 2004-2012 FX35
The total cost depends on whether you do the job yourself or hire a professional. The sensors themselves can be difficult to remove due to rust and heat, which can increase labor time.
| Part / Service | Estimated Cost (per sensor) |
|---|---|
| New OEM INFINITI Sensor | $220 - $400+ |
| New Aftermarket (Denso/NGK) | $139 - $181 |
| Shop Labor | $100 - $250 |
| Total Professional Replacement (Aftermarket) | $239 - $431 |
Frequently Asked Questions
How many Air/Fuel sensors does my FX35 have?
Your INFINITI FX35 has two upstream Air/Fuel Ratio sensors (Bank 1 and Bank 2) and two downstream oxygen sensors. Bank 1 is on the passenger side of the engine, and Bank 2 is on the driver's side.
Can I replace just one sensor?
Yes, you only need to replace the sensor that has failed. However, since they are the same age, it's not uncommon for the other sensor to fail soon after. Some owners choose to replace them in pairs as preventative maintenance, especially on higher-mileage vehicles.
Is this a difficult DIY job?
It can be. While unplugging and unscrewing the sensor is straightforward in theory, they are often seized in the exhaust manifold from years of heat and corrosion. A special slotted oxygen sensor socket is required, and you may need a torch to heat the manifold to break the sensor free. If you are not comfortable with this, it's best to leave it to a professional.
Are there any recalls for this part on my FX35?
No, there are no safety recalls issued by the NHTSA for the air/fuel ratio sensors on the 2004-2012 INFINITI FX35. Recalls for this vehicle range primarily concern airbags and a fuel filler hose on earlier models.
Technical Specifications
OEM Part Numbers: 22693-CD700 22693-1NA0A 22693-1MR0A
The INFINITI FX35 uses two wideband, heated, 4 or 5-wire air/fuel ratio sensors in the upstream positions (before the catalytic converters). Part numbers vary between the VQ35DE (2004-2008) and VQ35HR (2009-2012) engines.
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The information in this article is provided for general reference and educational purposes only. Vehicle specifications, procedures, and part compatibility can vary by production date, trim level, and region. Always consult your vehicle's factory service manual and verify part numbers before purchasing or performing repairs. Safety-critical components such as airbags, seat belts, and braking systems should be installed by a qualified professional.
- INFINITI FX35:
- 🛍️ Shop This Part
- Is Your INFINITI FX35 Air/Fuel Sensor Failing?
- Key Symptoms of a Bad A/F Sensor:
- Don't Mistake a MAF or Throttle Body Issue for a Bad Sensor
- Choosing the Right Aftermarket A/F Sensor
- Brand Quality: Denso and NGK/NTK
- Upstream vs. Downstream Sensors
- Cost of Replacing an Air/Fuel Ratio Sensor on a 2004-2012 FX35
- Frequently Asked Questions
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