NTK 25079 Oxygen Sensor - Downstream or Downstream Left

Direct Fit Oxygen Sensor for Audi Applications

NTK Oxygen Sensor Part Number 25079 is a direct fit heated oxygen sensor built for specific downstream left and downstream applications. It is engineered for Audi A4, A4 Quattro, A6, and A6 Quattro models where accurate exhaust feedback and OE-style fitment are required.

Key Features

• Direct fit, specific application oxygen sensor
• Heated sensor design for faster operating response
• 4-wire configuration with 23.2500 wiring harness length
• 18.000 thread diameter and threaded mounting type
• Built by NTK, a major OE oxygen sensor supplier
• Cross-references DENSO Auto Parts 234-4413 and Stant 15158 for the same application

Product Details

NTK Direct Fit Oxygen Sensor 25079 is part of the NTK product line focused on OE-style replacement sensors for import and domestic vehicles. NTK uses ceramic-based sensor manufacturing and extensive production testing to deliver fit, form, and function that align with original equipment requirements. This sensor is listed for downstream left and downstream positions on select Audi A4, Audi A4 Quattro, Audi A6, and Audi A6 Quattro models, including B2S2 locations noted in the fitment data.

Fits 2009-2011 Audi A6 Quattro, downstream left. Fits 2009 Audi A4 Quattro, downstream left. Fits 2006-2009 Audi A6, downstream. Fits 2007-2008 Audi A4, downstream left. Fits 2007-2008 Audi A4 Quattro, downstream left. Fits 2005-2008 Audi A6 Quattro, downstream. Fits 2006 Audi A4, downstream left. Fits 2006 Audi A4 Quattro, downstream left.

Common Issues This Sensor Can Address

• Check engine light related to oxygen sensor performance
• Incorrect air-fuel ratio feedback from a worn downstream sensor
• Slow sensor response after extended heat cycling
• Fault codes tied to B2S2 or downstream left sensor locations
• Emissions test failures caused by degraded exhaust monitoring

Installation Notes and Tips

Confirm the vehicle year, engine configuration, and sensor position before ordering. This is a specific-fit, threaded oxygen sensor with a 4-wire heated design, so connector routing and harness length should be matched to the original unit. On listed Audi A4, A4 Quattro, A6, and A6 Quattro applications, verify the downstream left or downstream location and any chassis breakpoints shown in the fitment notes.

Quality Assurance

NTK manufactures oxygen sensors to meet or exceed OE specifications and tests them during production for quality and reliability. As part of the NGK family of products, NTK supports original equipment and aftermarket coverage with OE application technology.