Infiniti M45 (2003-2010) Oxygen Sensor Replacement Guide
Fix your M45's check engine light and poor fuel economy by understanding its oxygen sensor system.
- Your M45 has four oxygen sensors; two upstream (air-fuel ratio) and two downstream (monitoring).
- Choose direct-fit sensors from OEM-equivalent brands like Denso or NGK for the best results.
- Ignoring a bad O2 sensor will decrease fuel economy and can lead to costly catalytic converter damage.
- Always use a diagnostic code to identify the specific failed sensor before purchasing a replacement.
Symptoms of a Failing Oxygen Sensor in Your M45
A bad oxygen sensor can cause noticeable problems. The most common sign is the check engine light turning on. You might also experience a significant drop in fuel economy, a rough idle, or hesitation when you accelerate. 🎬 Watch: Common symptoms of a failing oxygen sensor explained. In some cases, you may smell a "rotten egg" odor from the exhaust, which can indicate a failing sensor is causing the catalytic converter to work improperly.
Don't Ignore a Failing O2 Sensor
While you can still drive with a bad oxygen sensor, it's not recommended for long. Continuing to drive will result in poor fuel mileage and performance. More importantly, it can lead to expensive damage to your M45's catalytic converters, a repair that costs significantly more than replacing the sensors themselves.
Choosing the Right Aftermarket Oxygen Sensor
When shopping for a replacement, you'll find many brands available. For a luxury performance vehicle like the M45, it's best to choose a quality part to ensure proper engine function. It is critical to select a direct-fit sensor with the correct vehicle-specific connector. Universal, or "splice-in," sensors are cheaper but are not recommended as they can lead to poor connections and unreliable performance.
Brand Tiers for Infiniti M45
- OEM-Equivalent (Recommended): Brands like Denso and NGK (also sold as NTK) are often the original equipment manufacturers for Infiniti. Choosing one of these is like getting the dealer part without the dealer markup. They are engineered to the exact specifications of your M45's engine and are the safest bet for a first-time fix.
- Premium Aftermarket: Bosch and Delphi are top-tier automotive suppliers that produce high-quality oxygen sensors. Bosch invented the automotive oxygen sensor and is a leading global supplier. Delphi also produces OE-quality sensors tested to 150,000 miles. These are excellent and reliable choices.
- Standard Aftermarket: Brands like Walker Products, DriveWire, and others offer a more budget-friendly option. While functional, some forum discussions suggest their lifespan might not match that of premium or OEM-equivalent brands.
Upstream vs. Downstream Sensors
The upstream (before-catalyst) and downstream (after-catalyst) sensors are not interchangeable. The upstream sensors are more complex Air/Fuel Ratio sensors, while the downstream are simpler oxygen sensors. Always verify the exact position (e.g., Bank 1 Sensor 1, Bank 2 Sensor 2) before purchasing. Bank 1 is on the passenger's side of the engine, and Bank 2 is on the driver's side. Sensor 1 is upstream, and Sensor 2 is downstream.
Common Ordering Mistakes
The most frequent error is buying the wrong sensor for the position. Your M45 has four sensors in specific locations: Bank 1 Sensor 1 (Upstream, Passenger Side), Bank 1 Sensor 2 (Downstream, Passenger Side), Bank 2 Sensor 1 (Upstream, Driver Side), and Bank 2 Sensor 2 (Downstream, Driver Side). Always confirm which sensor has failed by reading the specific diagnostic trouble code (DTC) and purchase the corresponding part. Also, ensure you are buying a direct-fit sensor, not a universal one that requires cutting and splicing wires.
Cost to Replace an Infiniti M45 Oxygen Sensor
The cost can vary depending on the brand of the part and whether you do the work yourself or hire a professional.
| Item | Estimated Cost |
|---|---|
| New Aftermarket Oxygen Sensor | $40 - $178 per sensor |
| New OEM Oxygen Sensor | $175 - $361 per sensor |
| Shop Labor | $72 - $105 |
| Total Professional Replacement | $373 - $466 (for one sensor) |
Frequently Asked Questions (FAQ)
How many oxygen sensors does a 2003-2010 Infiniti M45 have?
All 2003-2010 Infiniti M45 models with the 4.5L V8 engine have four oxygen sensors: two upstream (air-fuel ratio sensors) and two downstream (monitoring sensors).
Can I replace just one oxygen sensor?
Yes. You only need to replace the sensor that has failed. A diagnostic scan tool will provide a specific code (like P0037, P0138, etc.) that points to the exact sensor and bank that needs replacement.
🎬 See how to fix a P0037 code on your M45.Is replacing an O2 sensor a difficult DIY job?
For a DIYer with some experience, it is a manageable job. The difficulty is often related to accessing the sensor, as some can be in tight spaces. You will need a special tool called an oxygen sensor socket, which has a slot for the wire. The sensors can also be rusted in place, requiring penetrating oil and patience to remove.
🎬 Watch this walkthrough of an M45 oxygen sensor replacement.Are there any recalls for the M45 oxygen sensors?
No, there are no specific recalls issued by Infiniti or the NHTSA for oxygen sensors on the 2003-2010 M45. However, recalls were issued for other components, such as for an inaccurate fuel gauge on 2003-2004 models.
Helpful Videos
Technical Specifications
OEM Part Numbers: 226A1-AR210 226A0-AR210 22691-AR210 22693-CD700 226A0-AM601 226A1-AM601
The 2003-2010 Infiniti M45 uses a total of four heated oxygen sensors. The two upstream sensors are wideband Air/Fuel Ratio sensors, and the two downstream sensors are conventional oxygen sensors for catalyst monitoring. All are direct-fit with vehicle-specific connectors.
We Have This Part in Stock
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 M45:
- 🎬 Helpful Videos
- 🛍️ Shop This Part
- Symptoms of a Failing Oxygen Sensor in Your M45
- Don't Ignore a Failing O2 Sensor
- Choosing the Right Aftermarket Oxygen Sensor
- Brand Tiers for Infiniti M45
- Upstream vs. Downstream Sensors
- Common Ordering Mistakes
- Cost to Replace an Infiniti M45 Oxygen Sensor
- Frequently Asked Questions (FAQ)
- 🎟️ Get 5% Off