NTK 25656 Oxygen Sensor

Direct Fit Oxygen Sensor for OE-Style Replacement

The NTK 25656 direct fit oxygen sensor is built for specific applications that require a heated, threaded, 4-wire replacement with OE-equivalent design. It is a practical choice for Audi A4, Audi A8 Quattro, Audi R8, Volkswagen GTI, and other listed vehicles needing accurate downstream or intermediate sensor service.

NTK’s Direct Fit Oxygen Sensor line is engineered for import and domestic coverage with application-specific fitment. As part of the NGK family of products, NTK applies ceramic manufacturing expertise and OE application knowledge to deliver sensors that match original equipment form, fit, and function.

Key Features

• Part number 25656 direct fit oxygen sensor for specific vehicle applications
• Heated sensor design for faster operating readiness
• 4-wire configuration for OE-style signal and heater circuit layout
• Threaded mounting with 18 mm thread diameter
• 31.5 in. wiring harness length for listed fitments
• Designed for downstream and intermediate positions where specified
• OE-equivalent design for direct replacement service

Detailed Description

NTK 25656 is a specific-fit oxygen sensor designed for vehicles that require a direct replacement in downstream or intermediate locations. It is listed for applications such as 2005-2009 Audi A4 and A4 Quattro, 2007-2010 Audi Q7, 2008-2011 Volkswagen GTI, and 2008-2010 Volkswagen Touareg, with fitment varying by engine bank and sensor position. This part cross-references Bosch (e.g., 16002, 16136) for the same application.

Built to meet OE-style requirements, this sensor supports accurate exhaust monitoring in vehicles such as the Audi A8 Quattro and Volkswagen Passat CC. The NTK 25656 is manufactured with ceramic control processes and tested during production to help maintain quality and reliability aligned with original equipment expectations.

What This Sensor Helps Address

• Check engine light related to oxygen sensor performance
• Fault codes tied to downstream or intermediate sensor readings
• Slow heater response in a heated oxygen sensor circuit
• Incorrect air-fuel feedback from a worn sensor
• Emissions inspection failures caused by sensor degradation

Installation Notes and Tips

Confirm the exact year, make, model, engine bank, and sensor position before ordering. This part is listed for downstream, downstream left, downstream right, and intermediate locations depending on application, so match the vehicle’s OE sensor placement to the fitment table. Use the threaded mounting specification and harness length to verify routing and connector reach before installation.

For best results, inspect the exhaust threads and wiring path before replacing the sensor. The NTK 25656 is a direct fit oxygen sensor, so it is intended to replace the original sensor without universal adaptation on the listed vehicles.

Quality Assurance

NTK is a major original equipment oxygen sensor manufacturer, and this Direct Fit Oxygen Sensor line is manufactured and tested to meet or exceed OE specifications for fit, form, and function. The brand’s focus on ceramic technology and application coverage supports consistent replacement quality across import applications.