NTK 21539 Oxygen Sensor

NTK 21539 Direct Fit Oxygen Sensor

NTK 21539 is a direct fit heated oxygen sensor built for specific applications that require OE-style placement, connector fit, and signal response. It is designed for upstream and downstream positions across a wide range of GM vehicles, including Buick LeSabre, Chevrolet Impala, and GMC Yukon applications.

As part of NTK’s Direct Fit Oxygen Sensor line, this replacement sensor is engineered for straightforward installation on the original mounting point and wiring layout. NTK’s focus on ceramic sensor technology and OE application coverage supports consistent fit, form, and function for emission control service.

Key Features

• Specific-fit oxygen sensor for direct replacement service
• Heated sensor design for faster operating temperature
• 4-wire configuration with threaded mounting
• 18 mm thread diameter
• 15.25 in. wiring harness length
• OE-style design for upstream and downstream locations
• Cross-references DENSO Auto Parts 234-4018 and Delphi ES20000 for the same application

Detailed Description

NTK 21539 oxygen sensor is engineered for emission control systems that rely on accurate exhaust gas feedback to manage air-fuel ratio and catalyst monitoring. It is a direct fit replacement for many 1996-2003 GM platforms, including Buick Century, Chevrolet Camaro, Chevrolet Silverado 1500, GMC Sierra 1500, and Pontiac Grand Prix applications. Depending on the vehicle, it serves upstream positions such as Bank 1 Sensor 1 or Bank 2 Sensor 1, as well as downstream locations including Bank 1 Sensor 2 and Bank 2 Sensor 2.

NTK manufactures oxygen sensors with OE-level application coverage and extensive production testing to help ensure reliable operation. This part number, 21539, is built for vehicles that require a threaded, heated sensor with the correct harness length and wire count for factory-style replacement.

What It Helps Address

• Check engine light related to oxygen sensor performance
• Incorrect air/fuel ratio readings
• Slow sensor response during closed-loop operation
• Emissions test failures tied to sensor output
• Fault codes for upstream or downstream O2 sensor circuits

Installation Notes and Tips

Verify the sensor position before ordering, since this application covers multiple upstream and downstream locations across different GM models and years. Confirm the connector style, harness length, and thread size against the original sensor before installation. For best results, inspect the exhaust threads and wiring routing, and follow the vehicle service manual for torque and connector placement.

Quality Assurance

NTK is a major original equipment oxygen sensor manufacturer with a long history of OE application support. The brand’s manufacturing process includes testing intended to meet or exceed OE specifications for fit and reliability. This part number, 21539, reflects NTK’s direct-fit approach for import and domestic emission control service.