NTK 25614 Oxygen Sensor

Direct-Fit Oxygen Sensor

NTK oxygen sensor 25614 is a specific-fit, heated sensor built for direct replacement applications. It uses a threaded mounting design and a 4-wire configuration with a 29.5-inch harness for a clean OE-style service fit.

Compatible With BMW and Mercedes-Benz applications that call for a downstream or upstream oxygen sensor, this part number 25614 supports precise air-fuel feedback and emissions system operation. NTK’s Direct Fit Oxygen Sensor line is built around OE application coverage and streamlined replacement selection.

Key Features

• Heated oxygen sensor for faster operating response
• Specific-fit design for direct replacement service
• Threaded mounting type for secure installation
• 4-wire construction for signal and heater circuit operation
• 29.5-inch wiring harness for application-specific routing
• 18 mm thread diameter

Detailed Description

NTK 25614 is an emission control oxygen sensor engineered for direct-fit replacement where the original sensor uses a threaded, heated, 4-wire design. The sensor is listed for BMW 740i, 740Li, 535i, 535i xDrive, 535xi, and X6 applications, as well as Mercedes-Benz SLK55 AMG, C240, C320, CLK320, CLK430, and CLK55 AMG applications in the fitment data. Depending on the vehicle, it serves downstream or upstream positions with OE-equivalent design notes included in the application listing.

As part of NTK’s Direct Fit Oxygen Sensor line, this part number 25614 reflects the brand’s focus on OE application coverage and manufacturing control from raw ceramic material through finished sensor. It is tested during production to meet or exceed OE specifications for fit, form, and function. This part cross-references Bosch (e.g., 16002, 16030) for the same application.

What It Is Used For

• Replacing a failed oxygen sensor that triggers emissions-related fault codes
• Restoring accurate exhaust oxygen feedback to the engine control system
• Addressing rough running caused by incorrect air-fuel ratio readings
• Correcting slow sensor response in heated oxygen sensor circuits
• Resolving drivability issues tied to worn or contaminated sensor elements

Installation Notes and Tips

Verify the exact year, model, and sensor position before ordering, since fitment varies by BMW and Mercedes-Benz application. Match the threaded mounting style, 4-wire layout, and harness length to the original sensor configuration. Use the fitment notes to confirm upstream or downstream placement and bank/sensor designation where listed.

Quality Assurance

NTK states that its 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.