NTK 21558 Oxygen Sensor

Direct Fit Oxygen Sensor for OE Replacement

NTK 21558 is a direct fit heated oxygen sensor built for specific applications that require OE-style fit, form, and function. It is engineered for upstream air/fuel ratio monitoring on select Chevrolet, GMC, Buick, Cadillac, Pontiac, Saturn, Saab, and Isuzu vehicles, including applications such as the Chevrolet Equinox, GMC Terrain, and Buick Lucerne.

Key Features

• Direct fit oxygen sensor with specific vehicle application coverage
• Heated sensor design for faster operating temperature
• 4-wire configuration with a 16.5 in. wiring harness length
• Threaded mounting type with 18 mm thread diameter
• OE-style design for upstream Bank 1 Sensor 1 applications
• Built by NTK, the Sensor Specialist and a major OE oxygen sensor manufacturer

Product Details

NTK Direct Fit Oxygen Sensor 21558 is designed for precise replacement on import and domestic vehicles that use an upstream heated oxygen sensor. NTK develops its ceramic sensor technology from raw material through finished product, and each sensor is extensively tested during manufacturing to help ensure quality and reliability that meet or exceed OE specifications. This part cross-references DENSO Auto Parts (e.g., 234-4242, 234-4339) for the same application.

Fitment includes 2010-2014 Chevrolet Equinox, upstream; 2010-2014 GMC Terrain, upstream; 2006-2011 Buick Lucerne, upstream rear and upstream front; and 2006-2011 Cadillac DTS, upstream rear and upstream front. It also covers 2008-2010 Chevrolet Malibu, 2008-2010 Pontiac G6, 2008-2010 Saturn Sky, and 2008-2010 Saturn Vue, all in upstream positions. The NTK 21558 is also listed for 2006-2009 Chevrolet Trailblazer and GMC Envoy upstream left/right applications, plus related platforms such as the Saab 9-7x and Buick Rainier.

What This Sensor Helps Address

• Check engine light related to oxygen sensor performance
• Incorrect air/fuel ratio readings from a worn upstream sensor
• Slow sensor response during closed-loop fuel control
• Emissions test failures caused by degraded sensor output
• Rough idle or fuel trim issues tied to faulty O2 sensor data

Installation Notes and Tips

Verify the connector, wire count, thread size, and sensor position before installation. This part is a specific-fit, threaded heated oxygen sensor with a 4-wire layout, so matching the original sensor location is important. Confirm whether your vehicle uses an upstream Bank 1 Sensor 1 location or another listed upstream position before ordering. The NTK 21558 is commonly searched as an oxygen sensor for Chevrolet Equinox, GMC Terrain, and Buick Lucerne upstream replacement needs.

Quality Assurance

NTK is part of the NGK family of products and is recognized as a leading OE oxygen sensor supplier. The brand’s manufacturing process uses advanced ceramic control and full-line OE application support to deliver consistent sensor performance across covered applications. Part number 21558 is built to OE specifications for direct replacement use.