NTK 25621 Oxygen Sensor - Downstream, Downstream Left or Downstream Right

Direct Fit Oxygen Sensor Overview

The NTK 25621 is a direct fit heated oxygen sensor built for specific import applications that require threaded mounting and OE-style signal control. It is engineered for precise replacement on Audi, Volkswagen, Bentley, and related platforms where accurate exhaust feedback matters.

Use this NTK oxygen sensor when you need a specific-fit replacement that matches the original sensor layout and wiring configuration. The 59-inch harness, 4-wire design, and 18 mm thread diameter support straightforward replacement on covered applications.

Key Features

• Direct fit oxygen sensor for specific applications
• Heated sensor design for faster operating response
• 4-wire configuration for OE-style signal control
• 59-inch wiring harness for application-specific routing
• Threaded mounting with 18 mm thread diameter
• Fits Audi A6 Quattro, Audi S4, Audi Allroad Quattro, Volkswagen Touareg, and other covered applications

Fitment Details

Compatible with 2000-2002 Volkswagen Cabrio, downstream; 2001-2003 Volkswagen EuroVan, downstream; 2002-2004 Audi A6 Quattro, downstream left and downstream right; 2002-2005 Audi Allroad Quattro, downstream left and downstream right; 2003 Bentley Continental, downstream left and downstream right; 2004 Audi S4, downstream left and downstream right; 2004 Volkswagen R32, downstream left; 2004-2007 Volkswagen Touareg, downstream left; 2004-2009 Audi S4, downstream left and downstream right; 2005-2009 Audi A8 Quattro, downstream; 2005-2009 Audi A8 Quattro, downstream; 2005-2009 Audi A8 Quattro, downstream.

What It Helps Address

• Faulty oxygen sensor readings
• Check engine light concerns related to exhaust feedback
• Incorrect air-fuel mixture control
• Slow sensor response after warm-up
• Replacement needs for damaged threaded sensors or wiring

Installation Notes and Quality

Verify the connector, harness length, thread diameter, and sensor position before installation. This part cross-references Bosch 16982 and DENSO Auto Parts 234-4809 for the same application.

NTK is part of the NGK family and is recognized as a major original equipment oxygen sensor supplier. NTK 25621 oxygen sensors are extensively tested during manufacturing to meet or exceed OE specifications for fit, form, and function.