NTK 25528 Oxygen Sensor - Upstream

Direct Fit Oxygen Sensor

NTK 25528 is a specific-fit heated oxygen sensor built for direct replacement applications. It uses a threaded mounting design and a 4-wire configuration to match the original sensor layout on supported BMW applications.

Fits 1986-1987 BMW 735i, upstream. Fits 1987 BMW L6, upstream. Fits 1987 BMW L7, upstream. Fits 1986 BMW L7, upstream.

Key Features

• Heated oxygen sensor for faster operating response.
• Specific-fit design for direct replacement use.
• Threaded mounting type for OE-style installation.
• 4-wire configuration with a 61.75-inch harness length.
• 18 mm thread diameter.
• NTK 25528 is part of the Direct Fit Oxygen Sensor line.

Detailed Description

NTK 25528 is an emission control oxygen sensor engineered for supported BMW 735i, L6, and L7 applications. As a direct fit oxygen sensor, it is built to match the original sensor form and function, with a heated design, threaded mounting, and four-wire construction. The 61.75-inch harness length provides the needed reach for the listed upstream locations. NTK 25528 is also referenced by cross numbers including Bosch 13037 for the same application.

NTK’s Direct Fit Oxygen Sensor line focuses on application-specific coverage and OE-style replacement fitment. NTK 25528 reflects that approach with a specific-fit design intended to simplify replacement on the listed BMW applications while maintaining the sensor characteristics expected for proper air/fuel ratio feedback.

What It Is Used For

• Replacing a worn upstream oxygen sensor.
• Restoring air/fuel ratio feedback to the engine control system.
• Addressing oxygen sensor fault codes.
• Correcting drivability issues tied to inaccurate exhaust gas readings.
• Replacing a sensor with damaged wiring or connector reach.

Installation Notes and Tips

Verify the vehicle’s sensor location, thread size, wire count, and harness length before installation. This part uses a threaded mounting type and a specific-fit configuration, so confirm the original sensor matches the listed application details. Follow the vehicle service procedure for removal and installation.

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.