NTK 21039 Oxygen Sensor - Upstream

NTK 21039 Direct Fit Oxygen Sensor

NTK 21039 is a direct fit, non-heated oxygen sensor built for specific upstream applications. It uses a threaded mounting design with a 15.75-inch wiring harness and a single-wire configuration for OE-style replacement on select Saturn, Chevrolet, GMC, Isuzu, Oldsmobile, and Pontiac vehicles.

The NTK Direct Fit Oxygen Sensor line focuses on original-equipment style fit, form, and function. NTK applies ceramic sensor manufacturing expertise and extensive production testing to help deliver consistent signal performance and reliable operation in emissions control systems.

Key Features

• Direct fit oxygen sensor for specific applications
• Non-heated sensor design
• Threaded mounting type with 18 mm thread diameter
• 15.75-inch wiring harness length
• Single-wire configuration
• OE-style replacement for upstream Bank 1 Sensor 1 locations
• NTK part number 21039

Vehicle Fitment

• Fits 1995-2002 Saturn SC1, Upstream
• Fits 1995-2002 Saturn SC2, Upstream
• Fits 1995-2002 Saturn SL, Upstream
• Fits 1995-2002 Saturn SL1, Upstream
• Fits 1995-2002 Saturn SL2, Upstream
• Fits 1995-2001 Saturn SW2, Upstream
• Fits 1999-2000 Chevrolet S10, Upstream
• Fits 1999-2000 GMC Sonoma, Upstream
• Fits 1999-2000 Isuzu Hombre, Upstream
• Fits 1999 Chevrolet Cavalier, Upstream
• Fits 1999 Chevrolet Malibu, Upstream
• Fits 1999 Oldsmobile Alero, Upstream
• Fits 1999 Pontiac Grand Am, Upstream
• Fits 1999 Pontiac Sunfire, Upstream
• Fits 1995-1999 Saturn SW1, Upstream

What This Sensor Helps Address

• Check engine light related to oxygen sensor performance
• Incorrect air/fuel ratio readings at the upstream sensor
• Slow or unstable sensor response during closed-loop operation
• Emissions test failures tied to a worn oxygen sensor
• Driveability issues caused by inaccurate exhaust oxygen feedback

Installation Notes

Confirm the vehicle’s upstream Bank 1 Sensor 1 location before ordering. This NTK 21039 oxygen sensor uses a threaded mount and a specific-fit harness, so connector style, wire length, and sensor placement should match the original part. For 1999 Chevrolet Malibu and 1999 Pontiac Grand Am applications, verify the RC9 option code noted in the fitment data.

Cross-reference: Bosch 13022 and DENSO Auto Parts 234-1022 for the same application.

Quality Assurance

NTK is a major original-equipment oxygen sensor manufacturer, and this sensor is produced with ceramic technology and manufacturing controls that are tested to meet or exceed OE specifications. The NTK 21039 is built for direct replacement use in supported import and domestic applications.