NTK 25527 Oxygen Sensor - Upstream

Direct-Fit Oxygen Sensor

This NTK direct fit oxygen sensor is built for specific applications and uses a heated, threaded design for straightforward replacement. It is engineered for air/fuel ratio control and is backed by NTK’s OE-focused sensor expertise.

• Specific-fit oxygen sensor for direct replacement applications
• Heated sensor design for faster operating response
• 4-wire configuration with threaded mounting
• 56-inch wiring harness length for application-specific routing
• 18 mm thread diameter

Application Details

Fits 1991-1995 BMW 525i, upstream. Fits 1993 BMW 525iT, upstream. This part cross-references Bosch 13108 and DENSO Auto Parts 234-4685 for the same application. The part number 25527 is part of NTK’s Direct Fit Oxygen Sensor line, which focuses on streamlined coverage and OE-style fit, form, and function. For BMW 525i and BMW 525iT applications, this sensor supports accurate exhaust feedback for the engine management system.

What It Helps Address

• Check engine light related to oxygen sensor performance
• Incorrect air/fuel ratio feedback
• Slow sensor response from a worn heated sensor
• Faults tied to damaged wiring or connector wear
• Replacement needs for threaded, specific-fit sensor locations

Installation Notes and Tips

Confirm the upstream location and match the connector, thread diameter, and harness length to the original sensor before installation. Use the vehicle’s service information to verify the correct bank and sensor position. The threaded mounting style is intended for direct replacement on listed applications.

Quality Assurance

NTK tests these oxygen sensors during manufacturing to meet or exceed OE specifications. As part number 25527, this sensor reflects NTK’s OE supplier background and application-specific coverage for import and domestic vehicles.