NTK 21508 Oxygen Sensor - Downstream or Upstream

Direct Fit Oxygen Sensor for Suzuki and Geo

NTK Oxygen Sensor 21508 is a direct fit, heated oxygen sensor built for specific applications that require OE-style fit, form, and function. It is engineered for accurate exhaust feedback on vehicles such as the Suzuki Esteem, Suzuki Sidekick, Suzuki X-90, Geo Tracker, Pontiac Sunrunner, and Chevrolet Tracker.

Key Features

• Heated oxygen sensor with specific fitment for direct replacement
• 4-wire design with a 20.5-inch wiring harness length
• Threaded mounting type with 18 mm thread diameter
• OE-equivalent design for upstream and downstream applications listed below
• NTK direct fit oxygen sensor part number 21508

Product Details

NTK is a long-established sensor manufacturer focused on oxygen sensor technology for import and domestic vehicles. The NTK Direct Fit Oxygen Sensor line is built to streamline replacement selection while maintaining OE application coverage. Part number 21508 uses ceramic-based sensor technology developed under NTK’s manufacturing expertise and is extensively tested during production for quality and reliability. This oxygen sensor is listed for 1993-2002 Suzuki Esteem, 1993-1998 Suzuki Sidekick, 1996-1998 Suzuki X-90, 1993-1998 Geo Tracker, 1996-1997 Geo Tracker, 1996-1997 Pontiac Sunrunner, 1994-1995 Pontiac Sunrunner, and 1998 Chevrolet Tracker in the positions shown below.

This part cross-references Bosch 13073 and DENSO Auto Parts 234-4060 for the same application.

What It Helps Address

• Check engine light related to oxygen sensor performance
• Incorrect air-fuel ratio feedback to the engine control module
• Slow sensor response from a worn heated oxygen sensor
• Emissions test failures tied to upstream or downstream sensor faults
• Rough idle or drivability issues caused by inaccurate exhaust readings

Installation Notes and Fitment

• Fits 1995-2002 Suzuki Esteem, upstream
• Fits 1996-2002 Suzuki Esteem, downstream
• Fits 1998 Chevrolet Tracker, upstream
• Fits 1996-1998 Suzuki Sidekick, upstream
• Fits 1996-1998 Suzuki X-90, upstream
• Fits 1996-1997 Geo Tracker, upstream
• Fits 1996-1997 Pontiac Sunrunner, upstream
• Fits 1993-1995 Geo Tracker, upstream
• Fits 1994-1995 Pontiac Sunrunner, upstream
• Fits 1994-1995 Suzuki Sidekick, upstream
• Fits 1993 Suzuki Sidekick, upstream

Verify connector routing, sensor location, and thread engagement before installation. This NTK 21508 oxygen sensor is a specific-fit replacement, so matching the listed position and application is important for proper installation.

Quality Assurance

NTK manufactures oxygen sensors with OE application coverage and production testing to help ensure consistent fit and reliable operation. As part of the NGK family of products, NTK supports import and domestic sensor applications with OE-style replacement coverage.