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NTK 25645 Oxygen Sensor - Downstream Left or Downstream Right
| Brand | NTK 25645 |
|---|---|
| Position | Downstream Right and Downstream Left |
| Wiring Harness Length | 63.7500 |
| Sensor Type | Heated |
| Universal Or Specific Fit | Specific |
| Wire Quantity | 4 |
| Thread Diameter | 18.000 |
| Mounting Type | Threaded |
| Product line | Direct Fit Oxygen Sensor |
| Fits | Audi · 6 vehicles |
Direct-fit design. Application-specific replacement for a precise sensor match.
Heated sensor. Built for faster operating response and stable signal performance.
OE-focused engineering. NTK applies original equipment sensor expertise to this replacement part.
Cross-references Bosch 16073, DENSO Auto Parts 234-4812 and Remy 16404 for the same application. See all 16.
Will it fit your vehicle?
Free return shipping if it doesn't fit.
Direct-fit oxygen sensor
NTK Oxygen Sensor 25645 is a direct-fit, heated oxygen sensor built for specific applications. It is engineered for threaded mounting and uses a 4-wire design with a 63.7500 wiring harness length for a precise replacement on compatible vehicles.
Key features
- Heated oxygen sensor for faster operating response.
- Specific-fit design for direct replacement applications.
- Threaded mounting with an 18.000 thread diameter.
- 4-wire configuration for the correct signal setup.
- 63.7500 wiring harness length for application-specific routing.
Detailed description
NTK 25645 is part of the Direct Fit Oxygen Sensor line, which focuses on application-specific replacement parts rather than universal coverage. NTK draws on its OE sensor manufacturing background to deliver fit, form, and function that align with original equipment requirements. This oxygen sensor is listed for 2001-2003 Audi A8 Quattro applications in downstream left and downstream right positions, making it a targeted replacement for those emission control locations. The part number 25645 is also useful when cross-checking catalog listings and service references.
This part cross-references Bosch 16073 and DENSO Auto Parts 234-4812 for the same application.
What it is used for
- Replacing a worn or slow-responding oxygen sensor.
- Restoring proper exhaust gas feedback to the engine control system.
- Addressing sensor fault codes related to oxygen sensor performance.
- Correcting drivability issues tied to inaccurate air-fuel monitoring.
- Replacing a damaged threaded sensor with the correct fitment.
Installation notes and tips
Verify the downstream left or downstream right position before ordering. Confirm the 4-wire connector style, threaded mounting, and harness length against the original sensor on the vehicle. For 2001-2003 Audi A8 Quattro applications, match the OE-equivalent placement and sensor configuration to avoid fitment errors.
Quality assurance
NTK states that these oxygen sensors are extensively tested during manufacturing and built to meet or exceed OE specifications. The brand is part of the NGK family of products and is recognized as a major original equipment oxygen sensor supplier.
| Year | Make | Model | Liters | Cylinders | Position | Notes |
|---|---|---|---|---|---|---|
| 2003 | Audi | A8 Quattro | 4.2L | V8 | Downstream Right | Downstream oxygen sensor with original equipment equivalent design; Direct Fit Oxygen Sensor |
| 2003 | Audi | A8 Quattro | 4.2L | V8 | Downstream Left | Oxygen Sensor B2S2 placement designed to OE specifications.; Direct Fit Oxygen Sensor |
| 2002 | Audi | A8 Quattro | 4.2L | V8 | Downstream Right | Downstream oxygen sensor with original equipment equivalent design; Direct Fit Oxygen Sensor |
| 2002 | Audi | A8 Quattro | 4.2L | V8 | Downstream Left | Oxygen Sensor B2S2 placement designed to OE specifications.; Direct Fit Oxygen Sensor |
| 2001 | Audi | A8 Quattro | 4.2L | V8 | Downstream Right | Downstream oxygen sensor with original equipment equivalent design; Direct Fit Oxygen Sensor |
| 2001 | Audi | A8 Quattro | 4.2L | V8 | Downstream Left | Oxygen Sensor B2S2 placement designed to OE specifications.; Direct Fit Oxygen Sensor |
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