NTK 25552 Oxygen Sensor - Downstream Left or Downstream Right

Direct Fit Oxygen Sensor for Audi and Volkswagen

NTK 25552 is a direct fit heated oxygen sensor built for specific downstream applications. It uses a threaded mounting design and a 4-wire configuration to match the original sensor layout on supported Audi and Volkswagen models.

• Direct fit oxygen sensor for specific applications
• Heated sensor design for faster operating response
• 4-wire construction with threaded mounting
• 68-inch wiring harness length
• 18 mm thread diameter

Fitment and Application Details

Compatible with 1996-1999 Audi A4, downstream right and downstream left; 1996-1999 Audi A4 Quattro, downstream right and downstream left; 1998-1999 Audi A6, downstream right and downstream left; 1998-1999 Audi A6 Quattro, downstream right and downstream left; and 1998-2000 Volkswagen Passat, downstream right and downstream left. This part number, 25552, is also referenced for OE-style replacement applications across these vehicles.

NTK’s Direct Fit Oxygen Sensor line is built to streamline coverage while maintaining OE-style fit, form, and function. As part of the NGK family, NTK applies ceramic manufacturing expertise and production testing to support consistent sensor performance across import and domestic applications.

What This Sensor Helps Address

• Faulty oxygen sensor readings
• Check engine light concerns related to sensor performance
• Slow sensor response from a worn heated sensor
• Incorrect air-fuel feedback from a failing downstream sensor
• Fitment issues caused by a non-specific replacement part

Installation Notes and Quality

Verify the connector style, wire count, thread diameter, and downstream position before installation. Confirm the vehicle build details for 1998 Audi A6 and A6 Quattro applications, which use a serial-number-specific fitment note. NTK 25552 is extensively tested during manufacturing to meet or exceed OE specifications for quality and reliability.