A Guide to the Ignition Knock Sensor for the 2003-2010 INFINITI M45
Understanding how to diagnose and choose the right replacement knock sensor for your M45's V8 engine.
- Replacing the knock sensor sub-harness (Part # 24079-2Y000) is mandatory, as it is the most common failure point.
- Due to the high labor cost, use a top-tier aftermarket brand like NGK/NTK or Beck Arnley to avoid repeat repairs.
- The 2003-2004 M45 and 2006-2010 M45 use different knock sensors; verify the correct part for your year.
- This is a difficult repair requiring removal of the intake manifold; it is not recommended for a DIY beginner.
Understanding Knock Sensor Failure in Your M45
The V8 engine in the INFINITI M45 has two knock sensors located in the valley of the engine, underneath the intake manifold. Due to this location, they are exposed to extreme heat. Over time, the sensors themselves can fail, but it is very common for the wiring harness that connects them (often called the sub-harness) to become brittle and crack. This often leads to a poor connection and triggers a Check Engine Light, even if the sensors are still good. For this reason, it is highly recommended to replace the sub-harness any time you replace the knock sensors.
Check Engine Light Codes P0327 and P0332
The most common trouble codes associated with knock sensor failure on the M45 are P0327 (Knock Sensor 1 Circuit Low Input - Bank 1) and P0332 (Knock Sensor 2 Circuit Low Input - Bank 2). These codes mean the engine computer is seeing a weak or non-existent signal from one or both sensors. This is often caused by a failed sensor or a break in the wiring harness.
Choosing the Right Aftermarket Knock Sensor
Because replacing the knock sensors on the VK45DE engine is a labor-intensive job, choosing a high-quality part is critical to avoid doing the job twice. Saving a few dollars on a cheap sensor can cost you hundreds in repeat labor charges.
Brand Quality Tiers
- Tier 1: OEM-Equivalent Brands (NGK/NTK, Beck Arnley): Brands like NTK (a division of NGK) and Hitachi are often the original manufacturers for Infiniti's parts. Choosing one of these brands gives you a part that is on par with OEM quality, often for a lower price than the dealer. Beck Arnley is also a trusted brand that often sources parts from the original OEM suppliers.
- Tier 2: Reputable Aftermarket (Delphi, Standard Ignition, Walker Products): These brands have a long history of producing reliable aftermarket parts. While generally dependable, some forums mention that Nissan and Infiniti vehicles can be sensitive to non-OEM electronics. They are a solid choice if a Tier 1 brand is not available.
- Tier 3: Budget Brands (MTC, Global Parts, Facet, Holstein): These brands offer the lowest price point. However, for a part that requires hours of labor to access, the risk of premature failure is high. It is generally not recommended to use a budget-tier sensor for this specific repair on an M45.
Pro Tip: Always purchase a new knock sensor sub-harness (OEM part number 24079-2Y000) when replacing your sensors. The old harness is the most common point of failure.
Common Ordering Mistakes to Avoid
There are two distinct generations of the M45 in this period, and they use different knock sensors. Be sure to order the correct part for your vehicle's year.
- 2003-2004 INFINITI M45 (Y34 generation)
- 2006-2010 INFINITI M45 (Y50 generation)
Always verify the part fits your specific year before ordering. Failing to replace the sub-harness at the same time is another frequent mistake that can lead to the same error code returning.
| Component | Estimated Cost |
|---|---|
| New Aftermarket Knock Sensor (Each) | $36 - $177 |
| New OEM Knock Sensor Sub-Harness | $60 - $90 |
| Shop Labor | $305 - $448 |
| Total Professional Replacement | $477 - $979 (using aftermarket sensors) |
Frequently Asked Questions (FAQ)
Can I replace just one knock sensor?
While you can replace only the failing sensor, the significant labor required to access the parts makes it wise to replace both sensors and the sub-harness at the same time. The second sensor and harness have been exposed to the same heat and are likely near the end of their service life.
Is there a recall on the INFINITI M45 knock sensor?
No, there are no specific recalls from Infiniti or the NHTSA for the knock sensors on the 2003-2010 M45. There were recalls for other sensors like the camshaft/crankshaft position sensors and the accelerator pedal sensor, but not the knock sensor.
What happens if I don't replace a bad knock sensor?
Your engine's computer will go into a "safe mode" to protect the engine. This typically results in noticeably reduced engine power, poor acceleration, and worse gas mileage. While the car is driveable, you will not have full performance, and you will fail an emissions test.
Why is the replacement so expensive?
The high cost is due to labor, not just the parts. The sensors are located deep in the engine valley, requiring the removal of the upper and lower intake manifolds to access them. This process can take a mechanic several hours.
Technical Specifications
OEM Part Numbers: 24079-2Y000 (Sub-Harness)
The INFINITI M45 uses two knock sensors located under the intake manifold. The sensors for the Y34 (2003-2004) and Y50 (2006-2010) generations are different and not interchangeable. The sub-harness that connects both sensors is a common point of failure.
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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 M45: